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Network Working Group                            S.E. Hardcastle-Kille
Internet Draft                               University College London
                                                         November 1991


         Mapping between X.400(1988) / ISO 10021 and RFC 822


Status of this Memo:

     This document describes a set of mappings which will  enable
     interworking  between  systems  operating  the  CCITT  X.400
     (1988) Recommendations on Message Handling Systems / ISO IEC
     10021  Message  Oriented  Text  Interchange  Systems (MOTIS)
     [CCITT/ISO88a], and systems using the RFC 822 mail  protocol
     [Crocker82a]   or  protocols  derived  from  RFC  822.   The
     approach aims to maximise the services  offered  across  the
     boundary, whilst not requiring unduly complex mappings.  The
     mappings should not require any changes to end systems. This
     document  is  a  revision based on RFCs 987, 1026, 1138, and
     1148[Kille86a,Kille87a] which  it obsoletes.

     This document specifies a  mapping  between  two  protocols.
     This  specification  should  be  used  when  this mapping is
     performed on the  DARPA  Internet  or  in  the  UK  Academic
     Community.  This  specification may be modified in the light
     of implementation experience, but no substantial changes are
     expected.

     This draft document  will be submitted to the RFC editor  as
     a  protocol  specification.   Distribution  of  this memo is
     unlimited.  Please send comments to the author.













Hardcastle-Kille                                              [page 1]







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                          Table of Contents




     1          - Overview ......................................    6

     1.1        - X.400 .........................................    6

     1.2        - RFC 822 .......................................    6

     1.3        - The need for conversion .......................    7

     1.4        - General approach ..............................    7

     1.5        - Gatewaying Model ..............................    8

     1.6        - X.400 (1984) ..................................   11

     1.7        - Compatibility with previous versions ..........   12

     1.8        - Aspects not covered ...........................   12

     1.9        - Subsetting ....................................   12

     1.10        - Document Structure ...........................   13

     1.11        - Acknowledgements .............................   13

     2          - Service Elements ..............................   14

     2.1        - The Notion of Service Across a Gateway ........   14

     2.2        - RFC 822 .......................................   15

     2.3        - X.400 .........................................   19

     3          - Basic Mappings ................................   30

     3.1        - Notation ......................................   30



Hardcastle-Kille                                              [page 2]







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     3.2        - ASCII and IA5 .................................   32

     3.3        - Standard Types ................................   32

     3.4        - Encoding ASCII in Printable String ............   35

     4          - Addressing ....................................   37

     4.1        - A textual representation of MTS.ORAddress .....   37

     4.2        - Basic Representation ..........................   37

     4.3        - EBNF.822-address <-> MTS.ORAddress ............   44

     4.4        - Repeated Mappings .............................   57

     4.5        - Directory Names ...............................   59

     4.6        - MTS Mappings ..................................   60

     4.7        - IPMS Mappings .................................   65

     5          - Detailed Mappings .............................   70

     5.1        - RFC 822 -> X.400 ..............................   70

     5.2        - Return of Contents ............................   78

     5.3        - X.400 -> RFC 822 ..............................   79

     Appendix A - Mappings Specific to SMTP .....................  107

     Appendix B - Mappings specific to the JNT Mail .............  108

     1          - Introduction ..................................  108

     2          - Domain Ordering ...............................  108

     3          - Addressing ....................................  108

     4          - Acknowledge-To:  ..............................  108

     5          - Trace .........................................  109




Hardcastle-Kille                                              [page 3]







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     6          - Timezone specification ........................  109

     7          - Lack of 822-MTS originator specification ......  109

     Appendix C - Mappings specific to UUCP Mail ................  111

     Appendix D - Object Identifier Assignment ..................  112

     Appendix E - BNF Summary ...................................  113

     Appendix F - Format of address mapping tables ..............  123

     1          - Global Mapping Information ....................  123

     2          - Syntax Definitions ............................  124

     3          - Table Lookups .................................  125

     4          - Domain -> O/R Address format ..................  125

     5          - O/R Address -> Domain format ..................  126

     6          - Domain -> O/R Address of Gateway table ........  126

     Appendix G - Mapping with X.400(1984) ......................  127

     Appendix H - RFC 822 Extensions for X.400 access ...........  129

     Appendix I - Conformance ...................................  130

          Appendix J - Change History: RFC 987, 1026, 1138,
          1148 ..................................................  132

     1          - Introduction ..................................  132

     2          - Service Elements ..............................  132

     3          - Basic Mappings ................................  133

     4          - Addressing ....................................  133

     5          - Detailed Mappings .............................  133

     6          - Appendices ....................................  134



Hardcastle-Kille                                              [page 4]







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     Appendix K - Change History: RFC 1148 to this Document
     ............................................................  135

     1          - General .......................................  135

     2          - Basic Mappings ................................  135

     3          - Addressing ....................................  135

     4          - Detailed Mappings .............................  136

     5          - Appendices ....................................  136



































Hardcastle-Kille                                              [page 5]






     Chapter 1 -- Overview



     1.1.  X.400

     This document relates to the CCITT 1988 X.400 Series
     Recommendations / ISO IEC 10021 on the Message Oriented Text
     Interchange Service (MOTIS).  This ISO/CCITT standard is referred
     to in this document as "X.400", which is a convenient shorthand.
     Any reference to the 1984 CCITT Recommendations will be explicit.
     X.400 defines an Interpersonal Messaging System (IPMS), making
     use of a store and forward Message Transfer System.  This
     document relates to the IPMS, and not to wider application of
     X.400.  It is expected that X.400 will be implemented very
     widely.

     1.2.  RFC 822

     RFC 822 evolved as a messaging standard on the DARPA (the US
     Defense Advanced Research Projects Agency) Internet.  It
     specifies and end to end message format.  It is used in
     conjunction with a number of different message transfer protocol
     environments.

     SMTP Networks
          On the DARPA Internet and other TCP/IP networks, RFC 822 is
          used in conjunction with two other standards: RFC 821, also
          known as Simple Mail Transfer Protocol (SMTP) [Postel82a],
          and RFC 920 which is a Specification for domains and a
          distributed name service [Postel84a].

     UUCP Networks
          UUCP is the UNIX to UNIX CoPy protocol, which is usually
          used over dialup telephone networks to provide a simple
          message transfer mechanism.  There are some extensions to
          RFC 822, particularly in the addressing.  They use domains
          which conform to RFC 920, but not the corresponding domain
          nameservers [Horton86a].




Hardcastle-Kille                                              [page 6]







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     Bitnet
          Some parts of Bitnet and related networks use RFC 822
          related protocols, with EBCDIC encoding.

     JNT Mail Networks
          A number of X.25 networks, particularly those associated
          with the UK Academic Community, use the JNT (Joint Network
          Team) Mail Protocol, also known as Greybook [Kille84a].
          This is used with domains and name service specified by the
          JNT NRS (Name Registration Scheme) [Larmouth83a].

     The mappings specified here are appropriate for all of these
     networks.

     1.3.  The need for conversion

     There is a large community using RFC 822 based protocols for mail
     services, who will wish to communicate with users of the IPMS
     provided by X.400 systems.  This will also be a requirement in
     cases where communities intend to make a transition to use of an
     X.400 IPMS, as conversion will be needed to ensure a smooth
     service transition.  It is expected that there will be more than
     one gateway, and this specification will enable them to behave in
     a consistent manner.  Note that the term gateway is used to
     describe a component performing the protocol mappings between RFC
     822 and X.400.  This is standard usage amongst mail implementors,
     but should be noted carefully by transport and network service
     implementors.

     Consistency between gateways is desirable to provide:

     1.   Consistent service to users.

     2.   The best service in cases where a message passes through
          multiple gateways.

     1.4.  General approach

     There are a number of basic principles underlying the details of
     the specification.  These principles are goals, and are not
     achieved in all aspects of the specification.

     1.   The specification should be pragmatic.  There should not be
          a requirement for complex mappings for "Academic" reasons.



Hardcastle-Kille                                              [page 7]







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          Complex mappings should not be required to support trivial
          additional functionality.

     2.   Subject to 1), functionality across a gateway should be as
          high as possible.

     3.   It is always a bad idea to lose information as a result of
          any transformation.  Hence, it is a bad idea for a gateway
          to discard information in the objects it processes.  This
          includes requested services which cannot be fully mapped.

     4.   All mail gateways actually operate at exactly one level
          above the layer on which they conceptually operate.  This
          implies that the gateway must not only be cognisant of the
          semantics of objects at the gateway level, but also be
          cognisant of higher level semantics.  If meaningful
          transformation of the objects that the gateway operates on
          is to occur, then the gateway needs to understand more than
          the objects themselves.

     5.   Subject to 1), the specification should be reversible.  That
          is, a double transformation should bring you back to where
          you started.

     1.5.  Gatewaying Model

     1.5.1.  X.400

     X.400 defines the IPMS Abstract Service in X.420/ISO 10021-7 ,
     [CCITT/ISO88b] which comprises of three basic services:

     1.   Origination

     2.   Reception

     3.   Management

     Management is a local interaction between the user and the IPMS,
     and is therefore not relevant to gatewaying.  The first two
     services consist of operations to originate and receive the
     following two objects:

     1.   IPM (Interpersonal Message). This has two components: a
          heading, and a body.  The body is structured as a sequence



Hardcastle-Kille                                              [page 8]







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          of body parts, which may be basic components (e.g., IA5
          text, or G3 fax), or IP Messages.  The heading consists of
          fields containing end to end user information, such as
          subject, primary recipients (To:), and importance.

     2.   IPN (Inter Personal Notification).  A notification  about
          receipt of a given IPM at the UA level.

     The Origination service also allows for origination of a probe,
     which is an object to test whether a given IPM could be correctly
     received.

     The Reception service also allows for receipt of Delivery Reports
     (DR), which indicate delivery success or failure.

          These IPMS Services utilise the Message Transfer (MT)
     Abstract Service [CCITT/ISO88c].  The MT Abstract Service
     provides the following three basic services:

     1.   Submission (used by IPMS Origination)

     2.   Delivery (used by IPMS Reception)

     3.   Administration (used by IPMS Management)

     Administration is a local issue, and so does not affect this
     standard.  Submission and delivery relate primarily to the MTS
     Message (comprising Envelope and Content), which carries an IPM
     or IPN (or other uninterpreted contents).  There is also an
     Envelope, which includes an ID, an originator, and a list of
     recipients.  Submission also includes the probe service, which
     supports the IPMS Probe. Delivery also includes Reports, which
     indicate whether a given MTS Message has been delivered or not.

          The MTS is REFINED into the MTA (Message Transfer Agent)
     Service, which defines the interaction between MTAs, along with
     the procedures for distributed operation.  This service provides
     for transfer of MTS Messages, Probes, and Reports.

     1.5.2.  RFC 822

     RFC 822 is based on the assumption that there is an underlying
     service, which is here called the 822-MTS service.  The 822-MTS
     service provides three basic functions:



Hardcastle-Kille                                              [page 9]







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     1.   Identification of a list of recipients.

     2.   Identification of an error return address.

     3.   Transfer of an RFC 822 message.

     It is possible to achieve 2) within the RFC 822 header.  Some
     822-MTS protocols, in particular SMTP, can provide additional
     functionality, but as these are neither mandatory in SMTP, nor
     available in other 822-MTS protocols, they are not considered
     here.  Details of aspects specific to two 822-MTS protocols are
     given in Appendices B and C.  An RFC 822 message consists of a
     header, and content which is uninterpreted ASCII text.  The
     header is divided into fields, which are the protocol elements.
     Most of these fields are analogous to P2 heading fields, although
     some are analogous to MTS Service Elements or MTA Service
     Elements.

     1.5.3.  The Gateway

     Given this functional description of the two services, the
     functional nature of a gateway can now be considered.  It would
     be elegant to consider the 822-MTS service mapping onto the MTS
     Service Elements and RFC 822 mapping onto an IPM, but reality
     just does not fit.  Another elegant approach would be to treat
     this document as the definition of an X.400 Access Unit (AU).
     Again, reality does not fit.  It is necessary to consider that
     the IPM format definition, the IPMS Service Elements, the MTS
     Service Elements, and MTA Service Elements on one side are mapped
     into RFC 822 + 822-MTS on the other in a slightly tangled manner.
     The details of the tangle will be made clear in Chapter 5.
     Access to the MTA Service Elements is minimised.

          The following basic mappings are thus defined.  When going
     from RFC 822 to X.400, an RFC 822 message and the associated
     822-MTS information is always mapped into an IPM (MTA, MTS, and
     IPMS Services).  Going from X.400 to RFC 822, an RFC 822 message
     and the associated 822-MTS information may be derived from:

     1.   A Report (MTA, and MTS Services)

     2.   An IPN (MTA, MTS, and IPMS services)

     3.   An IPM (MTA, MTS, and IPMS services)



Hardcastle-Kille                                             [page 10]







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     Probes (MTA Service) must be processed by the gateway, as
     discussed in Chapter 5.  MTS Messages containing Content Types
     other than those defined by the IPMS are not mapped by the
     gateway, and should be rejected at the gateway.

     1.5.4.  Repeated Mappings

     The primary goal of this specification is to support single
     mappings, so that X.400 and RFC 822 users can communicate with
     maximum functionality.

          The mappings specified here are designed to work where a
     message traverses multiple times between X.400 and RFC 822. This
     is often essential, particularly in the case of distribution
     lists.  However, in general, this will lead to a level of service
     which is the lowest common denominator (approximately the
     services offered by RFC 822).

          Some RFC 822 networks may wish to use X.400 as an
     interconnection mechanism (typically for policy reasons), and
     this is fully supported.

          Where an X.400 messages transfers to RFC 822 and then back
     to X.400, there is no expectation of X.400 services which do not
     have an equivalent service in standard RFC 822 being preserved -
     although this may be possible in some cases.

     1.6.  X.400 (1984)

     Much of this work is based on the initial specification of RFC
     987 and in its addendum RFC 1026, which defined a mapping between
     X.400(1984) and RFC 822.  A basic decision is that the mapping
     defined in this document is to the full 1988 version of X.400,
     and not to a 1984 compatible subset. New features of X.400(1988)
     can be used to provide a much cleaner mapping than that defined
     in RFC 987.  This is important, to give good support to
     communities which will utilise full X.400 at an early date.   To
     interwork with 1984 systems, Appendix G shall be followed.

          If a message is being transferred to an X.400(1984) system
     by way of X.400(1988) MTA it will give a slightly better service
     to follow the rules of Appendix G.





Hardcastle-Kille                                             [page 11]







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     1.7.  Compatibility with previous versions

     The changes between this an older versions of the document are
     given in Appendices I and J.    These are RFCs 987, 1026, 1138,
     and 1148.  This document is a revision of RFC 1148 [Kille90a].
     As far as possible, changes have been made in a compatible
     fashion.

     1.8.  Aspects not covered

     There have been a number of cases where RFC 987 was used in a
     manner which was not intended.  This section is to make clear
     some limitations of scope.  In particular, this specification
     does not specify:

     -    Extensions of RFC 822 to provide access to all X.400
          services

     -    X.400 user interface definition

     -    Mapping X.400 to extended versions of RFC 822, with support
          for multimedia content.

     The first two of these are really coupled.  To map the X.400
     services, this specification defines a number of extensions to
     RFC 822.  As a side effect, these give the 822 user access to
     SOME X.400 services.  However, the aim on the RFC 822 side is to
     preserve current service, and it is intentional that access is
     not given to all X.400 services.  Thus, it will be a poor choice
     for X.400 implementors to use RFC 987(88) as an interface - there
     are too many aspects of X.400 which cannot be accessed through
     it.  If a text interface is desired, a specification targeted at
     X.400, without RFC 822 restrictions, would be more appropriate.
     Some optional and limited extensions in this area have proved
     useful, and are defined in Appendix G.

     1.9.  Subsetting

     This proposal specifies a mapping which is appropriate to
     preserve services in existing RFC 822 communities.
     Implementations and specifications which subset this
     specification are strongly discouraged.





Hardcastle-Kille                                             [page 12]







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     1.10.  Document Structure

     This document has five chapters:

     1.   Overview - this chapter.

     2.   Service Elements - This describes the (end user) services
          mapped by a gateway.

     3.   Basic mappings - This describes some basic notation used in
          Chapters 3-5, the mappings between character sets, and some
          fundamental protocol elements.

     4.   Addressing - This considers the mapping between X.400 O/R
          names and RFC 822 addresses, which is a fundamental gateway
          component.

     5.   Detailed Mappings - This describes the details of all other
          mappings.

     There are also eleven appendices.



     WARNING:
          THE REMAINDER OF THIS SPECIFICATION IS TECHNICALLY DETAILED.
          IT WILL NOT MAKE SENSE, EXCEPT IN THE CONTEXT OF RFC 822 AND
          X.400 (1988).  DO NOT ATTEMPT TO READ THIS DOCUMENT UNLESS
          YOU ARE FAMILIAR WITH THESE SPECIFICATIONS.

     1.11.  Acknowledgements

     The work in this specification was substantially based on RFC 987
     and RFC 1148, which had input from many people, who are credited
     in the respective documents.

          A number of comments from people on RFC 1148 lead to this
     document.  In particular, there were comments and suggestions
     from:  Maurice Abraham (HP); Harald Alvestrand (Sintef); Peter
     Cowen (X-Tel); Jim Craigie (JNT); Christian Huitema (Inria); Erik
     Huizer (SURFnet); Neil Jones (DEC); Ignacio Martinez (IRIS);
     Julian Onions (X-Tel); Simon Poole (SWITCH); Clive Roberts (Data
     General); Pete Vanderbilt (SUN); Alan Young (Concurrent).




Hardcastle-Kille                                             [page 13]







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     Chapter 2 - Service Elements


     This chapter considers the services offered across a gateway
     built according to this specification.  It gives a view of the
     functionality provided by such a gateway for communication with
     users in the opposite domain.  This chapter considers service
     mappings in the context of SINGLE transfers only, and not
     repeated mappings through multiple gateways.


     2.1.  The Notion of Service Across a Gateway

     RFC 822 and X.400 provide a number of services to the end user.
     This chapter describes the extent to which each service can be
     supported across an X.400 <-> RFC 822 gateway.  The cases
     considered are single transfers across such a gateway, although
     the problems of multiple crossings are noted where appropriate.

     2.1.1.  Origination of Messages

     When a user originates a message, a number of services are
     available.  Some of these imply actions (e.g., delivery to a
     recipient), and some are insertion of known data (e.g.,
     specification of a subject field).  This chapter describes, for
     each offered service, to what extent it is supported for a
     recipient accessed through a gateway.  There are three levels of
     support:

     Supported
          The corresponding protocol elements map well, and so the
          service can be fully provided.

     Not Supported
          The service cannot be provided, as there is a complete
          mismatch.

     Partial Support
          The service can be partially fulfilled.

     In the first two cases, the service is simply marked as
     "Supported" or "Not Supported".  Some explanation may be given if
     there are additional implications, or the (non) support is not
     intuitive.  For partial support, the level of partial support is



Hardcastle-Kille                                             [page 14]







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     summarised.  Where partial support is good,  this will be
     described by a phrase such as "Supported by use of.....".  A
     common case of this is where the service is mapped onto a non-
     standard service on the other side of the gateway, and this would
     have lead to support if it had been a standard service.  In many
     cases, this is equivalent to support.  For partial support, an
     indication of the mechanism is given, in order to give a feel for
     the level of support provided.  Note that this is not a
     replacement for Chapter 5, where the mapping is fully specified.

          If a service is described as supported, this implies:

     -    Semantic correspondence.

     -    No (significant) loss of information.

     -    Any actions required by the service element.

     An example of a service gaining full support: If an RFC 822
     originator specifies a Subject:  field, this is considered to be
     supported, as an X.400 recipient will get a subject indication.

     In many cases, the required action will simply be to make the
     information available to the end user.  In other cases, actions
     may imply generating a delivery report.

          All RFC 822 services are supported or partially supported
     for origination.  The implications of non-supported X.400
     services is described under X.400.


     2.1.2.  Reception of Messages

     For reception, the list of service elements required to support
     this mapping is specified.  This is really an indication of what
     a recipient might expect to see in a message which has been
     remotely originated.

     2.2.  RFC 822

     RFC 822 does not explicitly define service elements, as distinct
     from protocol elements.  However, all of the RFC 822 header
     fields, with the exception of trace, can be regarded as
     corresponding to implicit RFC 822 service elements.



Hardcastle-Kille                                             [page 15]







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     2.2.1.  Origination in RFC 822

     A mechanism of mapping, used in several cases, is to map the RFC
     822 header into a heading extension in the IPM (InterPersonal
     Message).  This can be regarded as partial support, as it makes
     the information available to any X.400 implementations which are
     interested in these services. Communities which require
     significant RFC 822 interworking are recommended to require that
     their X.400 User Agents are able to display these heading
     extensions.  Support for the various service elements (headers)
     is now listed.

     Date:
          Supported.

     From:
          Supported.  For messages where there is also a sender field,
          the mapping is to "Authorising Users Indication", which has
          subtly different semantics to the general RFC 822 usage of
          From:.

     Sender:
          Supported.

     Reply-To:
          Supported.

     To:  Supported.

     Cc:  Supported.

     Bcc: Supported.

     Message-Id:
          Supported.

     In-Reply-To:
          Supported, for a single reference.  Where multiple
          references are given, partial support is given by mapping to
          "Cross Referencing Indication".  This gives similar
          semantics.

     References:
          Supported.



Hardcastle-Kille                                             [page 16]







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     Keywords:
          Supported by use of a heading extension.

     Subject:
          Supported.

     Comments:
          Supported by use of an extra body part.

     Encrypted:
          Supported by use of a heading extension.

     Resent-*
          Supported by use of a heading extension.  Note that
          addresses in these fields are mapped onto text, and so are
          not accessible to the X.400 user as addresses.  In
          principle, fuller support would be possible by mapping onto
          a forwarded IP Message, but this is not suggested.

     Other Fields
          In particular X-* fields, and "illegal" fields in common
          usage (e.g., "Fruit-of-the-day:") are supported by use of
          heading extensions.

     2.2.2.  Reception by RFC 822

     This considers reception by an RFC 822 User Agent of a message
     originated in an X.400 system and transferred across a gateway.
     The following standard services (headers) may be present in such
     a message:

     Date:

     From:

     Sender:

     Reply-To:

     To:

     Cc:

     Bcc:



Hardcastle-Kille                                             [page 17]







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     Message-Id:

     In-Reply-To:

     References:

     Subject:

     The following non-standard services (headers) may be present.
     These are defined in more detail in Chapter 5 (5.3.4, 5.3.6,
     5.3.7):

     Autoforwarded:

     Content-Identifier:

     Conversion:

     Conversion-With-Loss:

     Delivery-Date:

     Discarded-X400-IPMS-Extensions:

     Discarded-X400-MTS-Extensions:

     DL-Expansion-History:

     Deferred-Delivery:

     Expiry-Date:

     Importance:

     Incomplete-Copy:

     Language:

     Latest-Delivery-Time:

     Message-Type:

     Obsoletes:




Hardcastle-Kille                                             [page 18]







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     Original-Encoded-Information-Types:

     Originator-Return-Address:

     Priority:

     Reply-By:

     Requested-Delivery-Method:

     Sensitivity:

     X400-Content-Type:

     X400-MTS-Identifier:

     X400-Originator:

     X400-Received:

     X400-Recipients:

     2.3.  X.400

     2.3.1.  Origination in X.400

     When mapping services from X.400 to RFC 822 which are not
     supported by RFC 822, new RFC 822 headers are defined.  It is
     intended that these fields will be registered, and that co-
     operating RFC 822 systems may use them.  Where these new fields
     are used, and no system action is implied, the service can be
     regarded as being partially supported.  Chapter 5 describes how
     to map X.400 services onto these new headers.  Other elements are
     provided, in part, by the gateway as they cannot be provided by
     RFC 822.

          Some service elements are marked N/A (not applicable).
     There are five cases, which are marked with different comments:

     N/A (local)
          These elements are only applicable to User Agent / Message
          Transfer Agent interaction and so they cannot apply to RFC
          822 recipients.




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     N/A (PDAU)
          These service elements are only applicable where the
          recipient is reached by use of a Physical Delivery Access
          Unit (PDAU), and so do not need to be mapped by the gateway.

     N/A (reception)
          These services  are only applicable for reception.

     N/A (prior)
          If requested, this service must be performed prior to the
          gateway.

     N/A (MS)
          These services are only applicable to Message Store (i.e., a
          local service).

          Finally, some service elements are not supported.  In
     particular, the new security services are not mapped onto RFC
     822.  Unless otherwise indicated, the behaviour of service
     elements marked as not supported will depend on the criticality
     marking supplied by the user.  If the element is marked as
     critical for transfer or delivery, a non-delivery notification
     will be generated.  Otherwise, the service request will be
     ignored.

     2.3.1.1.  Basic Interpersonal Messaging Service

     These are the mandatory IPM services as listed in Section 19.8 of
     X.400 / ISO/IEC 10021-1, listed here in the order given. Section
     19.8 has cross references to short definitions of each service.

     Access management
          N/A (local).

     Content Type Indication
          Supported by a new RFC 822 header (Content-Type:).

     Converted Indication
          Supported by a new RFC 822 header (X400-Received:).

     Delivery Time Stamp Indication
          N/A (reception).

     IP Message Identification



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          Supported.

     Message Identification
          Supported, by use of a new RFC 822 header
          (X400-MTS-Identifier).  This new header is required, as
          X.400 has two message-ids whereas RFC 822 has only one (see
          previous service).

     Non-delivery Notification
          Not supported, although in general an RFC 822 system will
          return error reports by use of IP messages.  In other
          service elements, this pragmatic result can be treated as
          effective support of this service element.

     Original Encoded Information Types Indication
          Supported as a new RFC 822 header
          (Original-Encoded-Information-Types:).

     Submission Time Stamp Indication
          Supported.

     Typed Body
          Some types supported.  IA5 is fully supported.
          ForwardedIPMessage is supported, with some loss of
          information.  Other types get some measure of support,
          dependent on X.400 facilities for conversion to IA5.  This
          will only be done where content conversion is not
          prohibited.

     User Capabilities Registration
          N/A (local).

     2.3.1.2.  IPM Service Optional User Facilities

     This section describes support for the optional (user selectable)
     IPM services as listed in Section 19.9 of X.400 / ISO/IEC 10021-
     1, listed here in the order given.  Section 19.9 has cross
     references to short definitions of each service.

     Additional Physical Rendition
          N/A (PDAU).

     Alternate Recipient Allowed
          Not supported.  There is no RFC 822 service equivalent to



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          prohibition of alternate recipient assignment (e.g., an RFC
          822 system may freely send an undeliverable message to a
          local postmaster).  Thus, the gateway cannot prevent
          assignment of alternative recipients on the RFC 822 side.
          This service really means giving the user control as to
          whether or not an alternate recipient is allowed. This
          specification requires transfer of messages to RFC 822
          irrespective of this service request, and so this service is
          not supported.

     Authorising User's Indication
          Supported.

     Auto-forwarded Indication
          Supported as new RFC 822 header (Auto-Forwarded:).

     Basic Physical Rendition
          N/A (PDAU).

     Blind Copy Recipient Indication
          Supported.

     Body Part Encryption Indication
          Supported by use of a new RFC 822 header
          (Original-Encoded-Information-Types:), although in most
          cases it will not be possible to map the body part in
          question.

     Content Confidentiality
          Not supported.

     Content Integrity
          Not supported.

     Conversion Prohibition
          Supported.  In this case, only messages with IA5 body parts,
          other body parts which contain only IA5, and Forwarded IP
          Messages (subject recursively to the same restrictions),
          will be mapped.

     Conversion Prohibition in Case of Loss of Information
          Supported.

     Counter Collection



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          N/A (PDAU).

     Counter Collection with Advice
          N/A (PDAU).

     Cross Referencing Indication
          Supported.

     Deferred Delivery
          N/A (prior).  This service should always be provided by the
          MTS prior to the gateway.  A new RFC 822 header
          (Deferred-Delivery:) is provided to transfer information on
          this service to the recipient.

     Deferred Delivery Cancellation
          N/A (local).

     Delivery Notification
          Supported.  This is performed at the gateway.  Thus, a
          notification is sent by the gateway to the originator.  If
          the 822-MTS protocol is JNT Mail, a notification may also be
          sent by the recipient UA.

     Delivery via Bureaufax Service
          N/A (PDAU).

     Designation of Recipient by Directory Name
          N/A (local).

     Disclosure of Other Recipients
          Supported by use of a new RFC 822 header (X400-Recipients:).
          This is descriptive information for the RFC 822 recipient,
          and is not reverse mappable.

     DL Expansion History Indication
          Supported by use of a new RFC 822 header
          (DL-Expansion-History:).

     DL Expansion Prohibited
          Distribution List means MTS supported distribution list, in
          the manner of X.400.  This service does not exist in the RFC
          822 world.  RFC 822 distribution lists should be regarded as
          an informal redistribution mechanism, beyond the scope of
          this control.  Messages will be sent to RFC 822,



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          irrespective of whether this service is requested.
          Theoretically therefore, this service is supported, although
          in practice it may appear that it is not supported.

     Express Mail Service
          N/A (PDAU).

     Expiry Date Indication
          Supported as new RFC 822 header (Expiry-Date:).  In general,
          no automatic action can be expected.

     Explicit Conversion
          N/A (prior).

     Forwarded IP Message Indication
          Supported, with some loss of information.  The message is
          forwarded in an RFC 822 body, and so can only be interpreted
          visually.

     Grade of Delivery Selection
          N/A (PDAU)

     Importance Indication
          Supported as new RFC 822 header (Importance:).

     Incomplete Copy Indication
          Supported as new RFC 822 header (Incomplete-Copy:).

     Language Indication
          Supported as new RFC 822 header (Language:).

     Latest Delivery Designation
          Not supported.  A new RFC 822 header (Latest-Delivery-Time:)
          is provided, which may be used by the recipient.

     Message Flow Confidentiality
          Not supported.

     Message Origin Authentication
          N/A (reception).

     Message Security Labelling
          Not supported.




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     Message Sequence Integrity
          Not supported.

     Multi-Destination Delivery
          Supported.

     Multi-part Body
          Supported, with some loss of information, in that the
          structuring cannot be formalised in RFC 822.

     Non Receipt Notification Request
          Not supported.

     Non Repudiation of Delivery
          Not supported.

     Non Repudiation of Origin
          N/A (reception).

     Non Repudiation of Submission
          N/A (local).

     Obsoleting Indication
          Supported as new RFC 822 header (Obsoletes:).

     Ordinary Mail
          N/A (PDAU).

     Originator Indication
          Supported.

     Originator Requested Alternate Recipient
          Not supported, but is placed as comment next to address
          (X400-Recipients:).

     Physical Delivery Notification by MHS
          N/A (PDAU).

     Physical Delivery Notification by PDS
          N/A (PDAU).

     Physical Forwarding Allowed
          Supported by use of a comment in a new RFC 822 header
          (X400-Recipients:), associated with the recipient in



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          question.

     Physical Forwarding Prohibited
          Supported by use of a comment in a new RFC 822 header
          (X400-Recipients:), associated with the recipient in
          question.

     Prevention of Non-delivery notification
          Supported, as delivery notifications cannot be generated by
          RFC 822.  In practice, errors will be returned as IP
          Messages, and so this service may appear not to be supported
          (see Non-delivery Notification).

     Primary and Copy Recipients Indication
          Supported

     Probe
          Supported at the gateway (i.e., the gateway services the
          probe).

     Probe Origin Authentication
          N/A (reception).

     Proof of Delivery
          Not supported.

     Proof of Submission
          N/A (local).

     Receipt Notification Request Indication
          Not supported.

     Redirection Allowed by Originator
          Redirection means MTS supported redirection, in the manner
          of X.400.  This service does not exist in the RFC 822 world.
          RFC 822 redirection (e.g., aliasing) should be regarded as
          an informal redirection mechanism, beyond the scope of this
          control.  Messages will be sent to RFC 822, irrespective of
          whether this service is requested.  Theoretically therefore,
          this service is supported, although in practice it may
          appear that it is not supported.

     Registered Mail
          N/A (PDAU).



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     Registered Mail to Addressee in Person
          N/A (PDAU).

     Reply Request Indication
          Supported as comment next to address.

     Replying IP Message Indication
          Supported.

     Report Origin Authentication
          N/A (reception).

     Request for Forwarding Address
          N/A (PDAU).

     Requested Delivery Method
          N/A (local).   The services required must be dealt with at
          submission time.  Any such request is made available through
          the gateway by use of a comment associated with the
          recipient in question.

     Return of Content
          In principle, this is N/A, as non-delivery notifications are
          not supported.  In practice, most RFC 822 systems will
          return part or all of the content along with the IP Message
          indicating an error (see Non-delivery Notification).

     Sensitivity Indication
          Supported as new RFC 822 header (Sensitivity:).

     Special Delivery
          N/A (PDAU).

     Stored Message Deletion
          N/A (MS).

     Stored Message Fetching
          N/A (MS).

     Stored Message Listing
          N/A (MS).

     Stored Message Summary
          N/A (MS).



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     Subject Indication
          Supported.

     Undeliverable Mail with Return of Physical Message
          N/A (PDAU).

     Use of Distribution List
          In principle this applies only to X.400 supported
          distribution lists (see DL Expansion Prohibited).
          Theoretically, this service is N/A (prior).  In practice,
          because of informal RFC 822 lists, this service can be
          regarded as supported.

     2.3.2.  Reception by X.400

     2.3.2.1.  Standard Mandatory Services

     The following standard IPM mandatory  user facilities are
     required for reception of RFC 822 originated mail by an X.400 UA.


     Content Type Indication

     Delivery Time Stamp Indication

     IP Message Identification

     Message Identification

     Non-delivery Notification

     Original Encoded Information Types Indication

     Submission Time Stamp Indication

     Typed Body

     2.3.2.2.  Standard Optional Services

     The following standard IPM optional user facilities are required
     for reception of RFC 822 originated mail by an X.400 UA.

     Authorising User's Indication




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     Blind Copy Recipient Indication

     Cross Referencing Indication

     Originator Indication

     Primary and Copy Recipients Indication

     Replying IP Message Indication

     Subject Indication

     2.3.2.3.  New Services

     A new service "RFC 822 Header Field" is defined using the
     extension facilities.  This allows for any RFC 822 header field
     to be represented.  It may be present in RFC 822 originated
     messages, which are received by an X.400 UA.





























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     Chapter 3 Basic Mappings



     3.1.  Notation

     The X.400 protocols are encoded in a structured manner according
     to ASN.1, whereas RFC 822 is text encoded.  To define a detailed
     mapping, it is necessary to refer to detailed protocol elements
     in each format.  A notation to achieve this is described in this
     section.


     3.1.1.  RFC 822

     Structured text is defined according to the Extended Backus Naur
     Form (EBNF) defined in Section 2 of RFC 822 [Crocker82a].  In the
     EBNF definitions used in this specification, the syntax rules
     given in Appendix D of RFC 822 are assumed.  When these EBNF
     tokens are referred to outside an EBNF definition, they are
     identified by the string "822." appended to the beginning of the
     string (e.g., 822.addr-spec).  Additional syntax rules, to be
     used throughout this specification, are defined in this chapter.

     The EBNF is used in two ways.

     1.   To describe components of RFC 822 messages (or of 822-MTS
          components).  In this case, the lexical analysis defined in
          Section 3 of RFC 822 shall be used.  When these new EBNF
          tokens are referred to outside an EBNF definition, they are
          identified by the string "EBNF." appended to the beginning
          of the string (e.g., EBNF.bilateral-info).

     2.   To describe the structure of IA5 or ASCII information not in
          an RFC 822 message.  In these cases, tokens will either be
          self delimiting, or be delimited by self delimiting tokens.
          Comments and LWSP are not used as delimiters, except for the
          following cases, where LWSP may be inserted according to RFC
          822 rules.

     -         Around the ":" in all headers

     -         EBNF.labelled-integer




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     -         EBNF.object-identifier

     -         EBNF.encoded-info

          RFC 822  folding  rules are applied to all headers.

     3.1.2.  ASN.1

     An element is referred to with the following syntax, defined in
     EBNF:

             element         = service "." definition *( "." definition )
             service         = "IPMS" / "MTS" / "MTA"
             definition      = identifier / context
             identifier      = ALPHA *< ALPHA or DIGIT or "-" >
             context         = "[" 1*DIGIT "]"

     The EBNF.service keys are shorthand for the following service
     specifications:

     IPMS IPMSInformationObjects defined in Annex E of X.420 / ISO
          10021-7.

     MTS  MTSAbstractService defined in Section 9 of X.411 / ISO
          10021-4.

     MTA  MTAAbstractService defined in Section 13 of X.411 / ISO
          10021-4.

     The first EBNF.identifier identifies a type or value key in the
     context of the defined service specification.   Subsequent
     EBNF.identifiers identify a value label or type in the context of
     the first identifier (SET or SEQUENCE).  EBNF.context indicates a
     context tag, and is used where there is no label or type to
     uniquely identify a component.  The special EBNF.identifier
     keyword "value" is used to denote an element of a sequence.

     For example, IPMS.Heading.subject defines the subject element of
     the IPMS heading.  The same syntax is also used to refer to
     element values.  For example,
     MTS.EncodedInformationTypes.[0].g3Fax refers to a value of
     MTS.EncodedInformationTypes.[0] .





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     3.2.  ASCII and IA5

     A gateway will interpret all IA5 as ASCII.  Thus, mapping between
     these forms is conceptual.

     3.3.  Standard Types

     There is a need to convert between ASCII text, and some of the
     types defined in ASN.1 [CCITT/ISO88d].  For each case, an EBNF
     syntax definition is given, for use in all of this specification,
     which leads to a mapping between ASN.1, and an EBNF construct.
     All EBNF syntax definitions of ASN.1 types are in lower case,
     whereas ASN.1 types are referred to with the first letter in
     upper case.  Except as noted, all mappings are symmetrical.

     3.3.1.  Boolean

     Boolean is encoded as:

             boolean = "TRUE" / "FALSE"


     3.3.2.  NumericString

     NumericString is encoded as:

             numericstring = *DIGIT


     3.3.3.  PrintableString

     PrintableString is a restricted IA5String defined as:

             printablestring  = *( ps-char )
             ps-restricted-char      = 1DIGIT /  1ALPHA / " " / "'" / "+"
                                / "," / "-" / "." / "/" / ":" / "=" / "?"
             ps-delim         = "(" / ")"
             ps-char          = ps-delim / ps-restricted-char

     This can be used to represent real printable strings in EBNF.

     3.3.4.  T.61String

     In cases where T.61 strings are only used for conveying human



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     interpreted information, the aim of a mapping is  to render the
     characters appropriately in the remote character set, rather than
     to maximise reversibility.  For these cases, the mappings to IA5
     defined in CCITT Recommendation X.408 (1988) shall be used
     [CCITT/ISO88a].  These will then be encoded in ASCII.

          There is also a need to represent Teletex Strings in ASCII,
     for some aspects of O/R Address.  For these, the following
     encoding is used:

             teletex-string   = *( ps-char / t61-encoded )
             t61-encoded      = "{" 1* t61-encoded-char "}"
             t61-encoded-char = 3DIGIT

     Common characters are mapped simply.  Other octets are mapped
     using a quoting mechanism similar to the printable string
     mechanism.  Each octet is represented as 3 decimal digits.

     There are a number of places where a string may have a Teletex
     and/or Printable String representation.  The following BNF is
     used to represent this.

             teletex-and-or-ps = [ printablestring ] [ "*" teletex-string ]

     The natural mapping is restricted to EBNF.ps-char, in order to
     make the full BNF easier to parse.

     3.3.5.  UTCTime

     Both UTCTime and the RFC 822 822.date-time syntax contain:  Year
     (lowest two digits), Month, Day of Month, hour, minute, second
     (optional), and Timezone.  822.date-time also contains an
     optional day of the week, but this is redundant.  Therefore a
     symmetrical mapping can be made between these constructs.

     Note:
          In practice, a gateway will need to parse various illegal
          variants on 822.date-time.  In cases where 822.date-time
          cannot be parsed, it is recommended that the derived UTCTime
          is set to the value at the time of translation.

     When mapping to X.400, the UTCTime format which specifies the
     timezone offset shall be used.




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     When mapping to RFC 822, the 822.date-time format shall include a
     numeric timezone offset (e.g., +0000).

     When mapping time values, the timezone shall be preserved as
     specified.  The date shall not be normalised to any other
     timezone.

     3.3.6.  Integer

     A basic ASN.1 Integer will be mapped onto EBNF.numericstring.  In
     many cases ASN.1 will enumerate Integer values or use ENUMERATED.
     An EBNF encoding labelled-integer is provided. When mapping from
     EBNF to ASN.1, only the integer value is mapped, and the
     associated text is discarded.  When mapping from ASN.1 to EBNF,
     addition of an appropriate text label is strongly encouraged.

             labelled-integer ::= [ key-string ] "(" numericstring ")"

             key-string      = *key-char
             key-char        = <a-z, A-Z, 0-9, and "-">


     3.3.7.  Object Identifier

     Object identifiers are represented in a form similar to that
     given in ASN.1.  The order is the same as for ASN.1 (big-endian).
     The numbers are mandatory, and used when mapping from the ASCII
     to ASN.1.  The key-strings are optional.  It is recommended that
     as many strings as possible are generated when mapping from ASN.1
     to ASCII, to facilitate user recognition.

             object-identifier  ::= oid-comp object-identifier
                             | oid-comp

             oid-comp ::= [ key-string ] "(" numericstring ")"

     An example representation of an object identifier is:

             joint-iso-ccitt(2) mhs (6) ipms (1) ep (11) ia5-text (0)

             or

             (2) (6) (1)(11)(0)




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     3.4.  Encoding ASCII in Printable String

     Some information in RFC 822 is represented in ASCII, and needs to
     be mapped into X.400 elements encoded as printable string.  For
     this reason, a mechanism to represent ASCII encoded as
     PrintableString is needed.

          A structured subset of EBNF.printablestring is now defined.
     This shall be used to encode ASCII in the PrintableString
     character set.

             ps-encoded       = *( ps-restricted-char / ps-encoded-char )
             ps-encoded-char  = "(a)"               ; (@)
                              / "(p)"               ; (%)
                              / "(b)"               ; (!)
                              / "(q)"               ; (")
                              / "(u)"               ; (_)
                              / "(l)"               ; "("
                              / "(r)"               ; ")"
                              / "(" 3DIGIT ")"

     The 822.3DIGIT in EBNF.ps-encoded-char must have range 0-127, and
     is interpreted in decimal as the corresponding ASCII character.
     Special encodings are given for: at sign (@), percent (%),
     exclamation mark/bang (!), double quote ("), underscore (_), left
     bracket ((), and right bracket ()).  These characters, with the
     exception of round brackets, are not included in PrintableString,
     but are common in RFC 822 addresses.  The abbreviations will ease
     specification of RFC 822 addresses from an X.400 system.  These
     special encodings shall be interpreted in a case insensitive
     manner, but always generated in lower case.

          A reversible mapping between PrintableString and ASCII can
     now be defined.  The reversibility means that some values of
     printable string (containing round braces) cannot be generated
     from ASCII.  Therefore, this mapping must only be used in cases
     where the printable strings may only be derived from ASCII (and
     will therefore have a restricted domain).  For example, in this
     specification, it is only applied to a Domain Defined Attribute
     which will have been generated by use of this specification and a
     value such as "(" would not be possible.

          To encode ASCII as PrintableString, the EBNF.ps-encoded
     syntax is used, with all EBNF.ps-restricted-char mapped directly.



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     All other 822.CHAR are encoded as EBNF.ps-encoded-char.

          To encode PrintableString as ASCII, parse PrintableString as
     EBNF.ps-encoded, and then reverse the previous mapping.  If the
     PrintableString cannot be parsed, then the mapping is being
     applied in to an inappropriate value, and an error shall be given
     to the procedure doing the mapping. In some cases, it may be
     preferable to pass the printable string through unaltered.

     Some examples are now given.  Note the arrows which indicate
     asymmetrical mappings:

                     PrintableString           ASCII

                     'a demo.'         <->   'a demo.'
                     foo(a)bar         <->   foo@bar
                     (q)(u)(p)(q)      <->   "_%"
                     (a)               <->   @
                     (A)               ->    @
                     (l)a(r)           <->   (a)
                     (126)             <->   ~
                     (                 ->    (
                     (l)               <->   (
























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     Chapter 4 - Addressing


     Addressing is probably the trickiest problem of an X.400 <-> RFC
     822 gateway.  Therefore it is given a separate chapter.  This
     chapter, as a side effect, also defines a textual representation
     of an X.400 O/R Address.

          Initially we consider an address in the (human) mail user
     sense of "what is typed at the mailsystem to reference a mail
     user".  A basic RFC 822 address is defined by the EBNF
     EBNF.822-address:

             822-address     = [ route ] addr-spec

     In an 822-MTS protocol, the originator and each recipient are be
     considered to be defined by such a construct.  In an RFC 822
     header, the EBNF.822-address is encapsulated in the 822.address
     syntax rule, and there may also be associated comments.  None of
     this extra information has any semantics, other than to the end
     user.

          The basic X.400 O/R Address, used by the MTS for routing, is
     defined by MTS.ORAddress.  In IPMS, the MTS.ORAddress is
     encapsulated within IPMS.ORDescriptor.

          It can be seen that RFC 822 822.address must be mapped with
     IPMS.ORDescriptor, and that RFC 822 EBNF.822-address must be
     mapped with MTS.ORAddress.


     4.1.  A textual representation of MTS.ORAddress

     MTS.ORAddress is structured as a set of attribute value pairs.
     It is clearly necessary to be able to encode this in ASCII for
     gatewaying purposes.  All components shall be encoded, in order
     to guarantee return of error messages, and to optimise third
     party replies.

     4.2.  Basic Representation

     An O/R Address has a number of structured and unstructured
     attributes.  For each unstructured attribute, a key and an
     encoding is specified.  For structured attributes, the X.400



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     attribute is mapped onto one or more attribute value pairs.  For
     domain defined attributes, each element of the sequence will be
     mapped onto a triple (key and two values), with each value having
     the same encoding.  The attributes are as follows, with 1984
     attributes given in the first part of the table.  For each
     attribute, a reference is given, consisting of the relevant
     sections in X.402 / ISO 10021-2, and the extension identifier for
     88 only attributes:

       Attribute (Component)                 Key         Enc     Ref     Id

84/88 Attributes

MTS.CountryName                        C                 P     18.3.3
MTS.AdministrationDomainName           ADMD              P     18.3.1
MTS.PrivateDomainName                  PRMD              P     18.3.21
MTS.NetworkAddress                     X121              N     18.3.7
MTS.TerminalIdentifier                 T-ID              N     18.3.23
MTS.OrganizationName                   O                 P/T   18.3.9
MTS.OrganizationalUnitNames.value      OU                P/T   18.3.10
MTS.NumericUserIdentifier              UA-ID             N     18.3.8
MTS.PersonalName                       PN                P/T   18.3.12
MTS.PersonalName.surname               S                 P/T   18.3.12
MTS.PersonalName.given-name            G                 P/T   18.3.12
MTS.PersonalName.initials              I                 P/T   18.3.12
MTS.PersonalName
   .generation-qualifier               GQ                P/T   18.3.12
MTS.DomainDefinedAttribute.value       DD                P/T   18.1

88 Attributes

MTS.CommonName                         CN                P/T   18.3.2    1
MTS.TeletexCommonName                  CN                P/T   18.3.2    2
MTS.TeletexOrganizationName            O                 P/T   18.3.9    3
MTS.TeletexPersonalName                PN                P/T   18.3.12   4
MTS.TeletexPersonalName.surname        S                 P/T   18.3.12   4
MTS.TeletexPersonalName.given-name     G                 P/T   18.3.12   4
MTS.TeletexPersonalName.initials       I                 P/T   18.3.12   4
MTS.TeletexPersonalName
   .generation-qualifier               GQ                P/T   18.3.12   4
MTS.TeletexOrganizationalUnitNames
   .value                              OU                P/T   18.3.10   5





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MTS.TeletexDomainDefinedAttribute
   .value                              DD                P/T   18.1      6
MTS.PDSName                            PD-SERVICE        P     18.3.11   7
MTS.PhysicalDeliveryCountryName        PD-C              P     18.3.13   8
MTS.PostalCode                         PD-CODE           P     18.3.19   9
MTS.PhysicalDeliveryOfficeName         PD-OFFICE         P/T   18.3.14   10
MTS.PhysicalDeliveryOfficeNumber       PD-OFFICE-NUM     P/T   18.3.15   11
MTS.ExtensionORAddressComponents       PD-EXT-ADDRESS    P/T   18.3.4    12
MTS.PhysicalDeliveryPersonName         PD-PN             P/T   18.3.17   13
MTS.PhysicalDeliveryOrganizationName   PD-O              P/T   18.3.16   14
MTS.ExtensionPhysicalDelivery
   AddressComponents                   PD-EXT-DELIVERY   P/T   18.3.5    15
MTS.UnformattedPostalAddress           PD-ADDRESS        P/T   18.3.25   16
MTS.StreetAddress                      PD-STREET         P/T   18.3.22   17
MTS.PostOfficeBoxAddress               PD-BOX            P/T   18.3.18   18
MTS.PosteRestanteAddress               PD-RESTANTE       P/T   18.3.20   19
MTS.UniquePostalName                   PD-UNIQUE         P/T   18.3.26   20
MTS.LocalPostalAttributes              PD-LOCAL          P/T   18.3.6    21
MTS.ExtendedNetworkAddress
   .e163-4-address.number              NET-NUM           N     18.3.7    22
MTS.ExtendedNetworkAddress
   .e163-4-address.sub-address         NET-SUB           N     18.3.7    22
MTS.ExtendedNetworkAddress
   .psap-address                       NET-PSAP          X     18.3.7    22
MTS.TerminalType                       T-TY              I     18.3.24   23


     The following keys identify different EBNF encodings, which are
     associated with the ASCII representation of MTS.ORAddress.

                        Key         Encoding

                        P     printablestring
                        N     numericstring
                        T     teletex-string
                        P/T   teletex-and-or-ps
                        I     labelled-integer
                        X     presentation-address

     The BNF for presentation-address is taken from the specification
     "A String Encoding of Presentation Address" [Kille89a].

     In most cases, the EBNF encoding maps directly to the ASN.1
     encoding of the attribute.  There are a few exceptions. In cases



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     where an attribute can be encoded as either a PrintableString or
     NumericString (Country, ADMD, PRMD), either form is mapped into
     the BNF.  When generating ASN.1, the NumericString encoding shall
     be used if the string contains only digits.

     There are a number of cases where the P/T (teletex-and-or-ps)
     representation is used.  Where the key maps to a single
     attribute, this choice is reflected in the encoding of the
     attribute (attributes 10-21).  For most of the 1984 attributes
     and common name, there is a printablestring and a teletex
     variant.   This pair of attributes is mapped onto the single
     component here.  This will give a clean mapping for the common
     cases where only one form of the name is used.

          Recently, ISO has undertaken work to specify a string form
     of O/R Address [CCITT/ISO91a].  This has specified a number of
     string keywords for attributes.  As RFC 1148 was an input to this
     work, many of the keywords are the same.  To increase
     compatability, the following alternative values shall be
     recognised when mapping from RFC 822 to X.400.  These shall not
     be generated when mapping from X.400 to RFC 822.

                        Keyword          Alternative

                    ADMD               A
                    PRMD               P
                    GQ                 Q
                    X121               X.121
                    UA-ID              N-ID
                    PD-OFFICE-NUMBER   PD-OFFICE NUMBER

     When mapping from RFC 822 to X.400, the keywords: OU1, OU2, OU3,
     and OU4, shall be recognised.    If these are present, no keyword
     OU shall be present.  These will be treated as ordered values of
     OU.

     4.2.1.  Encoding of Personal Name

     Handling of Personal Name and Teletex Personal Name based purely
     on the EBNF.standard-type syntax defined above is likely to be
     clumsy.  It seems desirable to utilise the "human" conventions
     for encoding these components.  A syntax is defined, which is
     designed to provide a clean encoding for the common cases of O/R
     Address specification where:



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     1.   There is no generational qualifier

     2.   Initials contain only letters

     3.   Given Name does not contain full stop ("."), and is at least
          two characters long.

     4.   Surname does not contain full stop in the first two
          characters.

     5    If Surname is the only component, it does not contain full
          stop.

     The following EBNF is defined:

             encoded-pn      = [ given "." ] *( initial "." ) surname

             given           = 2*<ps-char not including ".">

             initial         = ALPHA

             surname         = printablestring

     This is used to map from any string containing only printable
     string characters to an O/R address personal name.  To map from a
     string to O/R Address components, parse the string according to
     the EBNF.  The given name and surname are assigned directly.  All
     EBNF.initial tokens are concatenated without intervening full
     stops to generate the initials component.

          For an O/R address which follows the above restrictions, a
     string is derived in the natural manner.  In this case, the















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     mapping will be reversible.

     For example:

             GivenName       = "Marshall"
             Surname         = "Rose"

             Maps with  "Marshall.Rose"

             Initials        = "MT"
             Surname         = "Rose"

             Maps with  "M.T.Rose"

             GivenName       = "Marshall"
             Initials        = "MT"
             Surname         = "Rose"

             Maps with  "Marshall.M.T.Rose"

     Note that X.400 suggest that Initials is used to encode ALL
     initials.  Therefore, the defined encoding is "natural" when
     either GivenName or Initials, but not both, are present.  The
     case where both are present can be encoded, but this appears to
     be contrived!

     4.2.2.  Standard Encoding of MTS.ORAddress

     Given this structure, we can specify a BNF representation of an
     O/R Address.

















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             std-or-address  = 1*( "/" attribute "=" value ) "/"
             attribute       = standard-type
                             / "RFC-822"
                             / registered-dd-type
                             / dd-key "." std-printablestring
             standard-type   = key-string

             registered-dd-type
                             = key-string
             dd-key          = key-string

             value           = std-printablestring

             std-printablestring
                             = *( std-char / std-pair )
             std-char        = <"{", "}", "*", and any ps-char
                                             except "/" and "=">
             std-pair        = "$" ps-char

     The standard-type is any key defined in the table in Section 4.2,
     except PN, and DD.  The BNF leads to a set of attribute/value
     pairs. The value is interpreted according to the EBNF encoding
     defined in the table.

          If the standard-type is PN, the value is interpreted
     according to EBNF.encoded-pn, and the components of
     MTS.PersonalName and/or MTS.TeletexPersonalName derived
     accordingly.

          If dd-key is the recognised Domain Defined string (DD), then
     the type and value are interpreted according to the syntax
     implied from the encoding, and aligned to either the teletex or
     printable string form.  Key and value shall have the same
     encoding.

          If value is "RFC-822", then the (printable string) Domain
     Defined Type of "RFC-822" is assumed.  This is an optimised
     encoding of the domain defined type defined by this
     specification.

          The matching of all keywords shall be done in a case-
     independent manner.




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          EBNF.std-or-address uses the characters "/" and "=" as
     delimiters.  Domain Defined Attributes and any value may contain
     these characters.  A quoting mechanism, using the non-printable
     string "$" is used to allow these characters to be represented.

          If the value is registered-dd-type, the value is registered
     at the IANA as an accepted Domain Defined Attribute type, then
     the value shall be interpreted accordingly.  This restriction
     maximises the syntax checking which can be done at a gateway.

     4.3.  EBNF.822-address <-> MTS.ORAddress

     Ideally, the mapping specified would be entirely symmetrical and
     global, to enable addresses to be referred to transparently in
     the remote system, with the choice of gateway being left to the
     Message Transfer Service.  There are two fundamental reasons why
     this is not possible:

     1.   The syntaxes are sufficiently different to make this
          awkward.

     2.   In the general case, there would not be the necessary
          administrative co-operation between the X.400 and RFC 822
          worlds, which would be needed for this to work.

     Therefore, an asymmetrical mapping is defined, which can be
     symmetrical where there is appropriate administrative control.

     4.3.1.  X.400 encoded in RFC 822

     The std-or-address syntax is  used to encode O/R Address
     information in the 822.local-part of EBNF.822-address.  In some
     cases, further  O/R Address information is associated with the
     822.domain component.  This cannot be used in the general case,
     due to character set problems, and to the variants of X.400 O/R
     Addresses which use different attribute types.  The only way to
     encode the full PrintableString character set in a domain is by
     use of the 822.domain-ref syntax (i.e. 822.atom).  This is likely
     to cause problems on many systems.  The effective character set
     of domains is in practice reduced from the RFC 822 set, by
     restrictions imposed by domain conventions and policy, and by
     restrictions in RFC 821.

          A generic 822.address consists of a 822.local-part and a



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     sequence of 822.domains (e.g., <@domain1,@domain2:user@domain3>).
     All except the 822.domain associated with the 822.local-part
     (domain3 in this case) are considered to specify routing within
     the RFC 822 world, and will not be interpreted by the gateway
     (although they may have identified the gateway from within the
     RFC 822 world).

          The  822.domain associated with the 822.local-part
     identifies the gateway from within the RFC 822 world.  This final
     822.domain may be used to determine some number of O/R Address
     attributes, where this does not conflict with the first role.
     RFC 822 routing to gateways will usually be set up to facilitate
     the 822.domain being used for both purposes.  The following O/R
     Address attributes are considered as a hierarchy, and may be
     specified by the domain.  They are (in order of hierarchy):

             Country, ADMD, PRMD, Organisation, Organisational Unit

     There may be multiple Organisational Units.

          A global mapping is defined between domain specifications,
     and some set of attributes.  This association proceeds
     hierarchically.  For example, if a domain implies ADMD, it also
     implies country.  Subdomains under this are associated according
     to the O/R Address hierarchy.  For example:

             => "AC.UK" might be associated with
             C="GB", ADMD="GOLD 400", PRMD="UK.AC"

             then domain "R-D.Salford.AC.UK" maps with
             C="GB", ADMD="GOLD 400", PRMD="UK.AC", O="Salford", OU="R-D"

     There are three basic reasons why a domain/attribute mapping
     might be maintained, as opposed to using simply subdomains:

     1.   As a shorthand to avoid redundant X.400 information.  In
          particular, there will often be only one ADMD per country,
          and so it does not need to be given explicitly.

     2.   To deal with cases where attribute values do not fit the
          syntax:






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             domain-syntax   = alphanum [ *alphanumhyphen alphanum ]
             alphanum        = <ALPHA or DIGIT>
             alphanumhyphen  = <ALPHA or DIGIT or HYPHEN>


          Although RFC 822 allows for a more general syntax, this
          restricted syntax is chosen as it is the one chosen by the
          various domain service administrations.

     3.   To deal with missing elements in the hierarchy.  A domain
          may be associated with an omitted attribute in conjunction
          with several present ones.  When performing the algorithmic
          insertion of components lower in the hierarchy, the omitted
          value shall be skipped.  For example, if "HNE.EGM" is
          associated with "C=TC", "ADMD=ECQ", "PRMD=HNE", and omitted
          organisation, then "ZI.HNE.EGM" is mapped with "C=TC",
          "ADMD=ECQ", "PRMD=HNE", "OU=ZI". Attributes may have null
          values, and  this is treated separately from omitted
          attributes (whilst it would be bad practice to treat these
          two cases differently, they must be allowed for).

          This set of mappings needs  be known by the gateways
     relaying between the RFC 822 world, and the O/R Address space
     associated with the mapping in question.  There needs to be a
     single global definition of this set of mappings.  A mapping
     implies an adminstrative equivalence between the two parts of the
     namespaces which are mapped together.  To correctly route in all
     cases, it is necessary for all gateways to know the mapping.  To
     facilitate distribution of a global set of mappings, a format for
     the exchange of this information is defined in Appendix F.

          The remaining attributes are encoded on the LHS, using the
     EBNF.std-or-address syntax.  For example:

             /I=J/S=Linnimouth/GQ=5/@Marketing.Widget.COM

     encodes the MTS.ORAddress consisting of:









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             MTS.CountryName                       = "TC"
             MTS.AdministrationDomainName          = "BTT"
             MTS.OrganizationName                  = "Widget"
             MTS.OrganizationalUnitNames.value     = "Marketing"
             MTS.PersonalName.surname              = "Linnimouth"
             MTS.PersonalName.initials             = "J"
             MTS.PersonalName.generation-qualifier = "5"

     The first three attributes are determined by the domain
     Widget.COM.  Then, the first element of OrganizationalUnitNames
     is determined systematically, and the remaining attributes are
     encoded on the LHS.  In an extreme case, all of the attributes
     will be on the LHS.  As the domain cannot be null, the RHS will
     simply be a domain indicating the gateway.

          The RHS (domain) encoding is designed to deal cleanly with
     common addresses, and so the amount of information on the RHS is
     maximised.  In particular, it covers the Mnemonic O/R Address
     using a 1984 compatible encoding.  This is seen as the dominant
     form of O/R Address.  Use of other forms of O/R Address, and
     teletex encoded attributes will require an LHS encoding.

          There is a further mechanism to simplify the encoding of
     common cases, where the only attributes to be encoded on the LHS
     is a (non-Teletex) Personal Name attributes which comply with the
     restrictions of 4.2.1.  To achieve this, the 822.local-part shall
     be encoded as EBNF.encoded-pn.  In the previous example, if the
     GenerationQualifier was not present, the encoding
     J.Linnimouth@Marketing.Widget.COM would result.

          From the standpoint of the RFC 822 Message Transfer System,
     the domain specification is simply used to route the message in
     the standard manner.  The standard domain mechanisms are used to
     select appropriate gateways for the corresponding O/R Address
     space.  In most cases, this will be done by registering the
     higher levels, and assuming that the gateway can handle the lower
     levels.

     4.3.2.  RFC 822 encoded in X.400

     In some cases, the encoding defined above may be reversed, to
     give a "natural" encoding of genuine RFC 822 addresses.  This
     depends largely on the allocation of appropriate management



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     domains.

          The general case is mapped by use of domain defined
     attributes.  A Domain defined type "RFC-822" is defined. The
     associated attribute value is an ASCII string encoded according
     to Section 3.3.3 of this specification. The interpretation of the
     ASCII string depends on the context of the gateway.

     1.   In the context of RFC 822, and RFC 920
          [Crocker82a,Postel84a], the string can be used directly.

     2.   In the context of the JNT Mail protocol, and the NRS
          [Kille84a,Larmouth83a], the string shall be interpreted
          according to Mailgroup Note 15 [Kille84b].

     3.   In the context of UUCP based systems, the string shall be
          interpreted as defined in [Horton86a].

          Other O/R Address attributes will be used to identify a
     context in which the O/R Address will be interpreted.  This might
     be a Management Domain, or some part of a Management Domain which
     identifies a gateway MTA.  For example:

             C               = "GB"
             ADMD            = "GOLD 400"
             PRMD            = "UK.AC"
             O               = "UCL"
             OU              = "CS"
             "RFC-822"      =  "Jimmy(a)WIDGET-LABS.CO.UK"

     OR

             C               = "TC"
             ADMD            = "Wizz.mail"
             PRMD            = "42"
             "rfc-822"       = "postel(a)venera.isi.edu"

     Note in each case the PrintableString encoding of "@" as "(a)".
     In the second example, the "RFC-822" domain defined attribute is
     interpreted everywhere within the (Private) Management Domain.
     In the first example, further attributes are needed within the
     Management Domain to identify a gateway.  Thus, this scheme can
     be used with varying levels of Management Domain co-operation.




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          There is a limit of 128 characters in the length of value of
     a domain defined attribute, and an O/R Address can have a
     maxmimum of four domain defined attributes.  Where the printable
     string generated from the RFC 822 address exceeeds this value,
     additional domain defined attributes are used to enable up to 512
     characters to be encoded.  These attributes shall be filled
     completely before the next one is started.   The DDA keywords
     are:  RFC822C1; RFC822C2; RFC822C3.  Longer addresses cannot be
     encoded.

          There is, analagous with 4.3.1, a means to associate parts
     of the O/R Address hierarchy with domains.  There is an analogous
     global mapping, which in most cases will be the inverse of the
     domain to O/R address mapping.  The mapping is maintained
     separately, as there may be differences (e.g., two alternate
     domain names map to the same set of O/R address components).

     4.3.3.  Component Ordering

     In most cases, ordering of O/R Address components is not
     significant for the mappings specified.  However, Organisational
     Units (printable string and teletex forms) and Domain Defined
     Attributes are specified as SEQUENCE in MTS.ORAddress, and so
     their order may be significant.  This specification needs to take
     account of this:

     1.   To allow consistent mapping into the domain hierarchy

     2.   To ensure preservation of order over multiple mappings.

     There are three places where an order is specified:

     1.   The text encoding (std-or-address) of MTS.ORAddress as used
          in the local-part of an RFC 822 address.  An order is needed
          for those components which may have multiple values
          (Organisational Unit, and Domain Defined Attributes). When
          generating an 822.std-or-address, components of a given type
          shall be in hierarchical order with the most significant
          component on the RHS.  If there is an Organisation
          Attribute, it shall be to the right of any Organisational
          Unit attributes.  These requirements are for the following
          reasons:

     -         Alignment to the hierarchy of other components in RFC



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               822 addresses (thus, Organisational Units will appear
               in the same order, whether encoded on the RHS or LHS).
               Note the differences of JNT Mail as described in
               Appendix B.

     -         Backwards compatibility with RFC 987/1026.

     -         To ensure that gateways generate consistent addresses.
               This is both to help end users, and to generate
               identical message ids.

          Further, it is recommended that all other attributes are
          generated according to this ordering, so that all attributes
          so encoded follow a consistent hierarchy.   When generating
          822.msg-id, this order shall be followed.

     2.   For the Organisational Units (OU) in MTS.ORAddress, the
          first OU in the SEQUENCE is the most significant, as
          specified in X.400.

     3.   For the Domain Defined Attributes in MTS.ORAddress, the
          First Domain Defined Attribute in the SEQUENCE is the most
          significant.

          Note that although this ordering is mandatory for this
          mapping, there are NO implications on ordering significance
          within X.400, where this is a Management Domain issue.

     4.3.4.  RFC 822 -> X.400

     There are two basic cases:

     1.   X.400 addresses encoded in RFC 822.  This will also include
          RFC 822 addresses which are given reversible encodings.

     2.   "Genuine" RFC 822 addresses.

     The mapping shall proceed as follows, by first assuming case 1).

     STAGE I.

     1.   If the 822-address is not of the form:

                  local-part "@" domain



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          take the domain which will be routed on and apply step 2 of
          stage 1 to derive (a possibly null) set of attributes. Then
          go to stage II.

          NOTE:It may be appropriate to reduce a source route address
               to this form by removal of all bar the last domain.  In
               terms of the design intentions of RFC 822, this would
               be an incorrect action.  However, in most real cases,
               it will do the "right" thing and provide a better
               service to the end user.  This is a reflection on the
               excessive and inappropriate use of source routing in
               RFC 822 based systems.  Either approach, or the
               intermediate approach of stripping only domain
               references which reference the local gateway are
               conformant to this specification.

     2.   Attempt to parse EBNF.domain as:

                  *( domain-syntax "." ) known-domain

          Where EBNF.known-domain is the longest possible match in the
          set of globally defined mappings (see Appendix F).  If this
          fails, and the EBNF.domain does not explicitly identify the
          local gateway, go to stage II.  If the domain explicitly
          identifies the gateway, allocate no attributes.  Otherwise,
          allocate the attributes associated with EBNF.known-domain.
          For each component, systematically allocate the attributes
          implied by each EBNF.domain-syntax component.  If this new
          component exceed an upper bound (ADMD: 16; PRMD: 16; O: 64;
          OU:  32) or it would lead to more than four OUs, then go to
          stage II with the attributes derived.

          At this stage, a set of attributes has been derived, which
          will give appropriate routing within X.400.  If any of the
          later steps of Stage I force use of Stage II, then these
          attributes should be used in Stage II.


     3.   If the 822.local-part contains any characters not in
          PrintableString, go to stage II.

     4.   If the 822.local-part uses the 822.quoted-string encoding,
          remove this quoting.  If this unquoted 822.local-part has
          leading space, trailing space, or two adjacent space go to



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          stage II.

     5.   Parse the (unquoted) 822.local-part according to the EBNF
          EBNF.std-or-address.  If this parse fails, parse the local-
          part according to the EBNF EBNF.encoded-pn.  If this parse
          fails, go to stage II.  The result is a set of type/value
          pairs.  If the values generated conflict with those derived
          in step 2 (e.g., a duplicated country attribute), the domain
          is assumed to be a remote gateway.  In this case, take only
          the LHS derived attributes, together with any RHS dericed
          attributes which are more significant thant the most
          signicant attribute which is duplicated (e.g., if there is a
          duplicate PRMD, but no LHS derived ADMD and country, then
          the ADMD and country should be taken from the RHS).
          therwise add LHS and RHS derived attributes together.

     6.   Associate the EBNF.attribute-value syntax (determined from
          the identified type) with each value, and check that it
          conforms.  If not, go to stage II.

     7.   Ensure that the set of attributes conforms both to the
          MTS.ORAddress specification and to the restrictions on this
          set given in X.400, and that no upper bounds are exceeded
          for any attribute.  If not go to stage II.

     8.   Build the O/R Address from this information.


     STAGE II.

     This will only be reached if the RFC 822 EBNF.822-address is not
     a valid X.400 encoding.  This implies that the address must refer
     to a recipient on an RFC 822 system.  Such addresses shall be
     encoded in an X.400 O/R Address using a domain defined attribute.

     1.   Convert the EBNF.822-address to PrintableString, as
          specified in Chapter 3.

     2.   Generate the "RFC-822" domain defined attribute  from this
          string.

     3.   Build the rest of the O/R Address in the manner described
          below.




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     It may not be possible to encode the domain defined attribute due
     to length restrictions.  If the limit is exceeded by a mapping at
     the MTS level, then the gateway shall reject the message in
     question.  If this occurs at the IPMS level, then the action will
     depend on the policy being taken for IPMS encoding, which is
     discussed in Section 5.1.3.

     If Stage I has identified a set of attributes, use these to build
     the remainder of the address.  The administrative equivalence of
     the mappings will ensure correct routing throug X.400 to a
     gateway back to RFC 822.

          If Stage I has not identified a set of attributes, the
     remainder of the O/R address effectively identifies a source
     route to a gateway from the X.400 side.  There are three cases,
     which are handled differently:

     822-MTS Return Address
          This shall be set up so that errors are returned through the
          same gateway.  Therefore, the O/R Address of the local
          gateway shall be used.

     IPMS Addresses
          These are optimised for replying.  In general, the message
          may end up anywhere within the X.400 world, and so this
          optimisation identifies a gateway appropriate for  the RFC
          822 address being converted.  The 822.domain to which the
          address would be routed is used to select an appropriate
          gateway. A globally defined set of mappings is used, which
          identifies (the O/R Address components of) appropriate
          gateways for parts of the domain namespace.  The longest
          possible match on the 822.domain defines which gateway to
          use.  The table format for distribution of this information
          is defined in Appendix F.

          This global mapping is used for parts of the RFC 822
          namespace which do not have an administrative equivalence
          with any part of the X.400 namespace, but for which it is
          desirable to identify a preferred X.400 gateway in order to
          optimise routing.

          If no mapping is found for the 822.domain, a default value
          (typically that of the local gateway) is used.  It is never
          appropriate to ignore the globally defined mappings.  In



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          some cases, it may be appropriate to locally override the
          globally defined mappings (e.g., to identify a gateway close
          to a recipient of the message).  This is likely to be where
          the global mapping identifies a public gateway, and the
          local gateway has an agreement with a private gateway which
          it prefers to use.

     822-MTS Recipient
          As the RFC 822 and X.400 worlds are fully connected, there
          is no technical reason for this situation to occur.  In some
          cases, routing may be configured to connect two parts of the
          RFC 822 world using X.400.  The information that this part
          of the domain space should be routed by X.400 rather than
          remaining within the RFC 822 world will be configured
          privately into the gateway in question.  The O/R address
          shall then be generated in the same manner as for an IPMS
          address, using the globally defined mappings. It is to
          support this case that the definition of the global domain
          to gateway mapping is important, as the use of this mapping
          will lead to a remote X.400 address, which can be routed by
          X.400 routing procedures.  The information in this mapping
          shall not be used as a basis for deciding to convert a
          message from RFC 822 to X.400.

     4.3.4.1.  Heuristics for mapping RFC 822 to X.400

     RFC 822 users will often use an LHS encoded address to identify
     an X.400 recipient.  Becuase the syntax is fairly complex, a
     number of heuristics may be applied to facilitate this form of
     usage.  A gateway should take care not to be overly "clever" with
     heuristics, as this may cause more confusion than a more
     mechanical approach.  The heuristics are as follows:

     1.   Ignore the omission of a trailing "/" in the std-or syntax.

     2.   If there is no ADMD component, and both country and PRMD are
          present, the value of /ADMD= / (single space) is assumed.

     3.   Parse the unquoted local part according to the EBNF colon-
          or-address.  This may facilitate users used to this
          delimiter.

          colon-or-address = 1*(attribute "=" value ";" *(LWSP-char))




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     The remaining heuristic relates to ordering of address
     components.  The ordering of attributes may be inverted or mixed.
     For this reason, the following heuristics may be applied:

     4.   If there is an Organisation attribute to the left of any Org
          Unit attribute, assume that the hierarchy is inverted.

     4.3.5.  X.400 -> RFC 822


     There are two basic cases:

     1.   RFC 822 addresses encoded in X.400.

     2.   "Genuine" X.400 addresses.  This may include symmetrically
          encoded RFC 822 addresses.

     When a MTS Recipient O/R Address is interpreted, gatewaying will
     be selected if there is a single "RFC-822" domain defined
     attribute present and the local gateway is identified by the
     remainder of the O/R Address.  In this case, use mapping A.  For
     other O/R Addresses which

     1.   Contain the special attribute.

          AND

     2.   Identifies the local gateway or any other known gateway with
          the other attributes.

     use mapping A.  In other cases, use mapping B.

     NOTE:
          A pragmatic approach would  be to assume that any O/R
          Address with the special domain defined attribute identifies
          an RFC 822 address. This will usually work correctly, but is
          in principle not correct.  Use of this approach is
          conformant to this specification.

     Mapping A

     1.   Map the domain defined attribute value to ASCII, as defined
          in Chapter 3.




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     Mapping B.

     This is used for X.400 addresses which do not use the explicit
     RFC 822 encoding.

     1.   For all string encoded attributes, remove any leading or
          trailing spaces, and replace adjacent spaces with a single
          space.

          The only attribute which is permitted to have zero length is
          the ADMD.  mapped to single space.      This should be
          mapped onto a single space.

          These transformations are for lookup only.   If an
          EBNF.std-or-address mapping is used as in 4), then the
          orginal values should be used.

     2.   Map numeric country codes to the two letter values.

     3.   Noting the hierarchy specified in 4.3.1, determine the
          maximum set of attributes which have an associated domain
          specification in the globally defined mapping.  If no match
          is found, allocate the domain as the domain specification of
          the local gateway, and go to step 5.

     Note:     It might be appropriate to use a non-local domain.
               This would be selected by a global mapping analagous to
               the one described at the end of 4.3.4.  This is not
               done, primarily because use of RFC 822 to connect X.400
               systems is not expected to be significant.

          In cases where the address refers to an X.400 UA, it is
          important that the generated domain will correctly route to
          a gateway.  In general, this is achieved by carefully co-
          ordinating RFC 822 routing with the definition of the global
          mappings, as there is no easy way for the gateway to make
          this check.  One rule that shall be used is that domains
          with only one component will not route to a gateway.  If the
          generated domain does not route correctly, the address is
          treated as if no match is found.

     4.   Following the 4.3.1 hierarchy,  noting any omitted
          components implied by the mapping used in 3). If each
          successive component exists, and conforms to the syntax



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          EBNF.domain-syntax (as defined in 4.3.1), allocate the next
          subdomain.  At least one attribute of the X.400 address
          shall not be mapped onto subdomain, as 822.local-part cannot
          be null.

     5.   If the remaining components are personal-name components,
          conforming to the restrictions of 4.2.1, then EBNF.encoded-
          pn is derived to form 822.local-part.  In other cases the
          remaining components are simply encoded as 822.local-part
          using the EBNF.std-or-address syntax.  If necessary, the
          822.quoted-string encoding is used.  The following are
          examples of legal quoting: "a b".c@x; "a b.c"@x.  Either
          form may be generated, but the latter is preferred.

          If the derived 822.local-part can only be encoded by use of
          822.quoted-string, then use of the mapping defined
          in[Kille89b] may be appropriate.  Use of this mapping is
          discouraged.

     4.4.  Repeated Mappings

     There are two types of repeated mapping:

     1.   A recursive mapping, where the repeat is within one gateway

     2    A source route, where the repetition occurs across multiple
          gateways

     4.4.1.  Recursive Mappings

     It is possible to supply an address which is recurive at a single
     gateway.  For example:

             C          = "XX"
             ADMD       = "YY"
             O          = "ZZ"
             "RFC-822"  = "Smith(a)ZZ.YY.XX"

     This is mapped first to an RFC 822 address, and then back to the
     X.400 address:







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             C          = "XX"
             ADMD       = "YY"
             O          = "ZZ"
             Surname    = "Smith"

     In some situations this type of recursion may be frequent.  It is
     important that where this occurs, that no unnecessary protocol
     conversion occurs. This will minimise loss of service.

     4.4.2.  Source Routes

     The mappings defined are symmetrical and reversible across a
     single gateway.  The symmetry is particularly useful in cases of
     (mail exploder type) distribution list expansion.  For example,
     an X.400 user sends to a list on an RFC 822 system which he
     belongs to.  The received message will have the originator and
     any 3rd party X.400 O/R Addresses in correct format (rather than
     doubly encoded).  In cases (X.400 or RFC 822) where there is
     common agreement on gateway identification, then this will apply
     to multiple gateways.

          When a message traverses multiple gateways, the mapping will
     always be reversible, in that a reply can be generated which will
     correctly reverse the path.  In many cases, the mapping will also
     be symmetrical, which will appear clean to the end user.  For
     example, if countries "AB" and "XY" have RFC 822 networks, but
     are interconnected by X.400, the following may happen:  The
     originator specifies:

             Joe.Soap@Widget.PTT.XY

     This is routed to a gateway, which generates:

             C               = "XY"
             ADMD            = "PTT"
             PRMD            = "Griddle MHS Providers"
             Organisation    = "Widget Corporation"
             Surname         = "Soap"
             Given Name      = "Joe"

     This is then routed to another gateway where the mapping is
     reversed to give:




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             Joe.Soap@Widget.PTT.XY

     Here, use of the gateway is transparent.

          Mappings will only be symmetrical where mapping tables are
     defined. In other cases, the reversibility is more important, due
     to the (far too frequent) cases where RFC 822 and X.400 services
     are partitioned.

          The syntax may be used to source route.  THIS IS STRONGLY
     DISCOURAGED.  For example:

             X.400 -> RFC 822  -> X.400

             C             = "UK"
             ADMD          = "Gold 400"
             PRMD          = "UK.AC"
             "RFC-822"     = "/PN=Duval/DD.Title=Manager/(a)Inria.ATLAS.FR"

     This will be sent to an arbitrary UK Academic Community gateway
     by X.400.  Then it will be sent by JNT Mail to another gateway
     determined by the domain Inria.ATLAS.FR (FR.ATLAS.Inria).  This
     will then derive the X.400 O/R Address:

             C             = "FR"
             ADMD          = "ATLAS"
             PRMD          = "Inria"
             PN.S          = "Duval"
             "Title"       = "Manager"

     Similarly:
     RFC 822 -> X.400 -> RFC 822

     "/C=UK/ADMD=BT/PRMD=AC/RFC-822=jj(a)seismo.css.gov/"@monet.berkeley.edu

     This will be sent to monet.berkeley.edu by RFC 822, then to the
     AC PRMD by X.400, and then to jj@seismo.css.gov by RFC 822.

     4.5.  Directory Names

     Directory Names are an optional part of O/R Name, along with O/R
     Address.  The RFC 822 addresses are mapped onto the O/R Address
     component. As there is no functional mapping for the Directory



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     Name on the RFC 822 side, a textual mapping is used.  There is no
     requirement for reversibility in terms of the goals of this
     specification.  There may be some loss of functionality in terms
     of third party recipients where only a directory name is given,
     but this seems preferable to the significant extra complexity of
     adding a full mapping for Directory Names.

     Note:There is ongoing work on specification of a "user friendly"
          format for directory names.  If this is adopted as an
          internet standard, it will be recommended, but not required,
          for use here.

     4.6.  MTS Mappings

     The basic mappings at the MTS level are:

     1) 822-MTS originator ->
                   MTS.PerMessageSubmissionFields.originator-name
        MTS.OtherMessageDeliveryFields.originator-name ->
                   822-MTS originator

     2) 822-MTS recipient ->
                   MTS.PerRecipientMessageSubmissionFields
        MTS.OtherMessageDeliveryFields.this-recipient-name ->
                   822-MTS recipient

     822-MTS recipients and return addresses are encoded as
     EBNF.822-address.

          The MTS Originator is always encoded as MTS.OriginatorName,
     which maps onto MTS.ORAddressAndOptionalDirectoryName, which in
     turn maps onto MTS.ORName.

     4.6.1.  RFC 822 -> X.400

     From the 822-MTS Originator, use the basic ORAddress mapping, to
     generate MTS.PerMessageSubmissionFields.originator-name
     (MTS.ORName), without a DirectoryName.

          For recipients, the following settings are made for each
     component of MTS.PerRecipientMessageSubmissionFields.

     recipient-name
          This is derived from the 822-MTS recipient by the basic



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          ORAddress mapping.

     originator-report-request
          This is be set according to content return policy, as
          discussed in Section 5.2.

     explicit-conversion
          This optional component is omitted, as this service is not
          needed

     extensions
          The default value (no extensions) is used

     4.6.2.  X.400 -> RFC 822

     The basic functionality is to generate the 822-MTS originator and
     recipients.  There is information present on the X.400 side,
     which cannot be mapped into analogous 822-MTS services.  For this
     reason, new RFC 822 fields are added for the MTS Originator and
     Recipients.  The information discarded at the 822-MTS level will
     be present in these fields. In some cases a (positive) delivery
     report will be gerated.

     4.6.2.1.  822-MTS Mappings

     Use the basic ORAddress mapping, to generate the 822-MTS
     originator (return address) from
     MTS.OtherMessageDeliveryFields.originator-name (MTS.ORName).  If
     MTS.ORName.directory-name is present, it is discarded.  (Note
     that it will be presented to the user, as described in 4.6.2.2).

          The 822-MTS recipient is conceptually generated from
     MTS.OtherMessageDeliveryFields.this-recipient-name.  This is done
     by taking MTS.OtherMessageDeliveryFields.this-recipient-name, and
     generating an 822-MTS recipient according to the basic ORAddress
     mapping, discarding MTS.ORName.directory-name if present.
     However, if this model was followed exactly, there would be no
     possibility to have multiple 822-MTS recipients on a single
     message.  This is unacceptable, and so layering is violated.  The
     mapping needs to use the MTA level information, and map each
     value of MTA.PerRecipientMessageTransferFields.recipient-name,
     where the responsibility bit is set, onto an 822-MTS recipient.





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     4.6.2.2.  Generation of RFC 822 Headers

     Not all per-recipient information can be passed at the 822-MTS
     level.  For this reason, two new RFC 822 headers are created, in
     order to carry this information to the RFC 822 recipient.  These
     fields are "X400-Originator:"  and "X400-Recipients:".

          The "X400-Originator:" field is set to the same value as the
     822-MTS originator.  In addition, if
     MTS.OtherMessageDeliveryFields.originator-name (MTS.ORName)
     contains MTS.ORName.directory-name then this Directory Name shall
     be represented in an 822.comment.

          Recipient names, taken from each value of
     MTS.OtherMessageDeliveryFields.this-recipient-name and
     MTS.OtherMessageDeliveryFields.other-recipient-names are made
     available to the RFC 822 user by use of the "X400-Recipients:"
     field.  By taking the recipients at the MTS level, disclosure of
     recipients will be dealt with correctly.  However, this conflicts
     with a desire to optimise mail transfer.  There is no problem
     when disclosure of recipients is allowed. Similarly, there is no
     problem if there is only one RFC 822 recipient, as the
     "X400-Recipients field is only given one address.

          There is a problem if there are multiple RFC 822 recipients,
     and disclosure of recipients is prohibited.  Two options are
     allowed:

     1.   Generate one copy of the message for each RFC 822 recipient,
          with the "X400-Recipients field correctly set to the
          recipient of that copy.  This is functionally correct, but
          is likely to be more expensive.

     2.   Discard the per-recipient information, and insert a field:

                  X400-Recipients: non-disclosure:;

          This is the recommended option.

     A third option of ignoring the disclosure flag is not allowed.
     If any MTS.ORName.directory-name is present, it shall be
     represented in an 822.comment.

          If



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     MTS.OtherMessageDeliveryFields.orignally-intended-recipient-name
     is present, then there has been redirection,  or there has been
     distribution list expansion.  Distribution list expansion is a
     per-message option, and the information associated with this is
     represented by the "DL-Expansion-History:" field descrined in
     Section 5.3.6.  Other information is represented in an
     822.comment associated associated with
     MTS.OtherMessageDeliveryFields.this-recipient-name, The message
     may be delivered to different RFC 822 recipients, and so several
     addresses in the "X400-Recipients:" field may have such comments.
     The non-commented recipient is the RFC 822 recipient. The EBNF of
     the comment is:

             redirect-comment  =
                      [ "Originally To:" ] mailbox "Redirected"
                      [ "Again" ] "on" date-time
                      "To:"  redirection-reason

             redirection-reason =
                      "Recipient Assigned Alternate Recipient"
                      / "Originator Requested Alternate Recipient"
                      / "Recipient MD Assigned Alternate Recipient"

     It is derived from
     MTA.PerRecipientMessageTransferFields.extension.redirection-history.
     An example of this is:

     X400-Recipients: postmaster@widget.com (Originally To:
           sales-manager@sales.widget.com Redirected
           on Thu, 30 May 91 14:39:40 +0100 To: Originator Assigned
           Alternate Recipient postmaster@sales.widget.com Redirected
           Again on Thu, 30 May 91 14:41:20 +0100 To: Recipient MD
           Assigned Alternate Recipient)



          In addition the following per-recipient services from
     MTS.OtherMessageDeliveryFields.extensions are represented in
     comments if they are used.  None of these services can be
     provided on RFC 822 networks, and so in general these will be
     informative strings associated with other MTS recipients. In some
     cases, string values are defined.  For the remainder, the string
     value shall be chosen by the implementor.   If the parameter has
     a default value, then no comment shall be inserted when the



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     parameter has that default value.

     requested-delivery-method

     physical-forwarding-prohibited
          "(Physical Forwarding Prohibited)".

     physical-forwarding-address-request
          "(Physical Forwarding Address Requested)".

     physical-delivery-modes

     registered-mail-type

     recipient-number-for-advice

     physical-rendition-attributes

     physical-delivery-report-request
          "(Physical Delivery Report Requested)".

     proof-of-delivery-request
          "(Proof of Delivery Requested)".

     4.6.2.3.  Delivery Report Generation

     If MTA.PerRecipientMessageTransferFields.per-recipient-indicators
     requires a positive delivery notification, this shall be
     generated by the gateway.  Supplementary Information shall be set
     to indicate that the report is gateway generated.

     4.6.3.  Message IDs (MTS)

     A mapping from 822.msg-id to MTS.MTSIdentifier is defined.  The
     reverse mapping is not needed, as MTS.MTSIdentifier is always
     mapped onto new RFC 822 fields.  The value of
     MTS.MTSIdentifier.local-part will facilitate correlation of
     gateway errors.

          To map from 822.msg-id, apply the standard mapping to
     822.msg-id, in order to generate an MTS.ORAddress.  The Country,
     ADMD, and PRMD components of this are used to generate
     MTS.MTSIdentifier.global-domain-identifier.
     MTS.MTSIdentifier.local-identifier is set to the 822.msg-id,



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     including the braces "<" and ">".   If this string is longer than
     MTS.ub-local-id-length (32), then it is truncated to this length.

          The reverse mapping is not used in this specification.  It
     would be applicable where MTS.MTSIdentifier.local-identifier is
     of syntax 822.msg-id, and it algorithmically identifies
     MTS.MTSIdentifier.

     4.7.  IPMS Mappings

     All RFC 822 addresses are assumed to use the 822.mailbox syntax.
     This includes all 822.comments associated with the lexical tokens
     of the 822.mailbox.  In the IPMS O/R Names are encoded as
     MTS.ORName.  This is used within the  IPMS.ORDescriptor,
     IPMS.RecipientSpecifier, and IPMS.IPMIdentifier.  An asymmetrical
     mapping is defined between these components.

     4.7.1.  RFC 822 -> X.400

     To derive IPMS.ORDescriptor from an RFC 822 address.

     1.   Take the address, and extract an EBNF.822-address.  This can
          be derived trivially from either the 822.addr-spec or
          822.route-addr syntax.  This is mapped to MTS.ORName as
          described above, and used as IMPS.ORDescriptor.formal-name.

     2.   A string shall be built consisting of (if present):

     -         The 822.phrase component if the 822.address is an
               822.phrase 822.route-addr construct.

     -         Any 822.comments, in order, retaining the parentheses.

          This string is then encoded into T.61 use a human oriented
          mapping (as described in Chapter 3).  If the string is not
          null, it is assigned to IPMS.ORDescriptor.free-form-name.

     3.   IPMS.ORDescriptor.telephone-number is omitted.

     If IPMS.ORDescriptor is being used in IPMS.RecipientSpecifier,
     IPMS.RecipientSpecifier.reply-request and
     IPMS.RecipientSpecifier.notification-requests are set to default
     values (none and false).




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          If the 822.group construct is present, any included
     822.mailbox is encoded as above to generate a separate
     IPMS.ORDescriptor.  The 822.group is  mapped to T.61, and a
     IPMS.ORDescriptor with only an free-form-name component built
     from it.

     4.7.2.  X.400 -> RFC 822

     Mapping from IPMS.ORDescriptor to RFC 822 address.  In the basic
     case, where IPMS.ORDescriptor.formal-name is present, proceed as
     follows.

     1.   Encode IPMS.ORDescriptor.formal-name (MTS.ORName) as
          EBNF.822-address.

     2a.  If IPMS.ORDescriptor.free-form-name is present, convert it
          to ASCII (Chapter 3), and use this as the 822.phrase
          component of 822.mailbox using the 822.phrase 822.route-addr
          construct.

     2b.  If IPMS.ORDescriptor.free-form-name is absent.  If
          EBNF.822-address is parsed as 822.addr-spec use this as the
          encoding of 822.mailbox.  If EBNF.822-address is parsed as
          822.route 822.addr-spec, then a 822.phrase taken from
          822.local-part is added.

     3    If IPMS.ORDescriptor.telephone-number is present, this is
          placed in an 822.comment, with the string "Tel ".  The
          normal international form of number is used.  For example:

                  (Tel +44-1-387-7050)


     4.   If IPMS.ORDescriptor.formal-name.directory-name is present,
          then a text representation is placed in a trailing
          822.comment.

     5.   If IPMS.RecipientSpecifier.report-request has any non-
          default values, then an 822.comment "(Receipt Notification
          Requested)", and/or "(Non Receipt Notification Requested)",
          and/or "(IPM Return Requested)" is appended to the address.
          The effort of correlating P1 and P2 information is too great
          to justify the gateway sending Receipt Notifications.




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     6.   If IPMS.RecipientSpecifier.reply-request is True, an
          822.comment "(Reply requested)"  is appended to the address.

     If IPMS.ORDescriptor.formal-name is absent,
     IPMS.ORDescriptor.free-form-name is converted to ASCII, and used
     as 822.phrase within the RFC 822 822.group syntax.  For example:

             Free Form Name ":" ";"

     Steps 3-6 are then followed.

     4.7.3.  IP Message IDs

     There is a need to map both ways between 822.msg-id and
     IPMS.IPMIdentifier.  This allows for X.400 Receipt Notifications,
     Replies, and Cross References to reference an RFC 822 Message ID,
     which is preferable to a gateway generated ID.  A reversible and
     symmetrical mapping is defined.  This allows for good things to
     happen when messages pass multiple times across the X.400/RFC 822
     boundary.

          An important issue with messages identifiers is mapping to
     the exact form, as many systems use these ids as uninterpreted
     keys.  The use of table driven mappings is not always
     symmetrical, particularly in the light of alternative domain
     names, and alternative management domains.  For this reason, a
     purely algorithmic mapping is used.  A mapping which is simpler
     than that for addresses can be used for two reasons:

     -    There is no major requirement to make message IDs "natural"

     -    There is no issue about being able to reply to message IDs.
          (For addresses, creating a return path which works is more
          important than being symmetrical).

     The mapping works by defining a way in which message IDs
     generated on one side of the gateway can be represented on the
     other side in a systematic manner.  The mapping is defined so
     that the possibility of clashes is is low enough to be treated as
     impossible.

     4.7.3.1.  822.msg-id represented in X.400

     IPMS.IPMIdentifier.user is omitted.  The



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     IPMS.IPMIdentifier.user-relative-identifier is set to a printable
     string encoding of the 822.msg-id with the angle braces ("<" and
     ">") removed.  The upper bound on this component is 64.  The
     options for handling this are discussed in Section 5.1.3.

     4.7.3.2.  IPMS.IPMIdentifier represented in RFC 822

     The 822.domain of 822.msg-id is set to the value "MHS". The
     822.local-part of 822.msg-id is built as

             [ printablestring ] "*"  [ std-or-address ]

     with EBNF.printablestring being the
     IPMS.IPMIdentifier.user-relative-identifier, and std-or-address
     being an encoding of the IPMS.IPMIdentifier.user.  If necessary,
     the 822.quoted-string encoding is used.  For example:

     <"147*/S=Dietrich/O=Siemens/ADMD=DBP/C=DE/"@MHS>


     4.7.3.3.  822.msg-id -> IPMS.IPMIdentifier

     If the 822.local-part can be parsed as:

             [ printablestring ] "*"  [ std-or-address ]

     and the 822.domain is "MHS", then this ID was X.400 generated.
     If EBNF.printablestring is present, the value is assigned to
     IPMS.IPMIdentifier.user-relative-identifier.  If
     EBNF.std-or-address is present, the O/R Address components
     derived from it are used to set IPMS.IPMIdentifier.user.

          Otherwise, this is an RFC 822 generated ID.  In this case,
     set IPMS.IPMIdentifier.user-relative-identifier to a printable
     string encoding of the 822.msg-id without the angle braces.

     4.7.3.4.  IPMS.IPMIdentifier -> 822.msg-id

          If IPMS.IPMIdentifier.user is absent, and
     IPMS.IPMIdentifier.user-relative-identifier mapped to ASCII and
     angle braces added parses as 822.msg-id, then this is an RFC 822
     generated ID.

          Otherwise, the ID is X.400 generated.  Use the



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     IPMS.IPMIdentifier.user to generate an EBNF.std-or-address form
     string.  Build the 822.local-part of the 822.msg-id with the
     syntax:

             [ printablestring ] "*"  [ std-or-address ]

     The printablestring is taken from
     IPMS.IPMIdentifier.user-relative-identifier.  Use
     822.quoted-string if necessary.  The 822.msg-id is generated with
     this 822.local-part, and "MHS" as the 822.domain.

     4.7.3.5.  Phrase form

     In "InReply-To:" and "References:", the encoding 822.phrase may
     be used as an alternative to 822.msg-id.  To map from 822.phrase
     to IPMS.IPMIdentifier, assign
     IPMS.IPMIdentifier.user-relative-identifier to the phrase.  When
     mapping from IPMS.IPMIdentifier for "In-Reply-To:" and
     "References:", if IPMS.IPMIdentifier.user is absent and
     IPMS.IPMIdentifier.user-relative-identifier does not parse as
     822.msg-id, generate an 822.phrase rather than adding the domain
     MHS.

     4.7.3.6.  RFC 987 backwards compatibility

     The mapping defined here is different to that used in RFC 987, as
     the RFC 987 mapping lead to changed message IDs in many cases.
     Fixing the problems is preferable to retaining backwards
     compatibility.  An implementation of this standard is encouraged
     to recognise message IDs generated by RFC 987.  This is not
     required.

          RFC 987 generated encodings may be recognised as follows.
     When mapping from X.400 to RFC 822, if the
     IPMS.IPMIdentifier.user-relative-identifier is "RFC-822" the id
     is RFC 987 generated. When mapping from RFC 822 to X.400, if the
     822.domain is not "MHS", and the 822.local-part can be parsed as

             [ printablestring ] "*"  [ std-or-address ]

     then it is RFC 987 generated.  In each of these cases, it is
     recommended to follow the RFC 987 rules.





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     Chapter 5 - Detailed Mappings


     This chapter specifies  detailed mappings for the functions
     outlined in Chapters 1 and 2.  It makes extensive use of the
     notations and mappings defined in Chapters 3 and 4.


     5.1.  RFC 822 -> X.400


     5.1.1.  Basic Approach

     A single IP Message is generated from an RFC 822 message The RFC
     822 headers are used to generate the IPMS.Heading.  The IP
     Message will have one IA5 IPMS.BodyPart containing the RFC 822
     message body.

          Some RFC 822 fields cannot be mapped onto a standard IPM
     Heading field, and so an extended field is defined in Section
     5.1.2.  This is then used for fields which cannot be mapped onto
     existing services.

          The message is submitted to the MTS, and the services
     required can be defined by specifying
     MTS.MessageSubmissionEnvelope.  A few parameters of the MTA
     Abstract service are also specified, which are not in principle
     available to the MTS User.  Use of these services allows RFC 822
     MTA level parameters to be carried in the analogous X.400 service
     elements.  The advantages of this mapping far outweigh the
     layering violation.

     5.1.2.  X.400 Extension Field

     An IPMS Extension is defined:

             rfc-822-field HEADING-EXTENSION
                     VALUE RFC822FieldList
                     ::= id-rfc-822-field-list


             RFC822FieldList ::= SEQUENCE OF RFC822Field

             RFC822Field ::= IA5String



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     The Object Identifier id-rfc-822-field-list is defined in
     Appendix D.

          To encode any RFC 822 Header using this extension, an
     RFC822Field element is built using the 822.field omitting the
     trailing CRLF (e.g., "Fruit-Of-The-Day: Kiwi Fruit"). Structured
     fields shall be unfolded.  There shall be no space before the
     ":".  The reverse mapping builds the RFC 822 field in a
     straightforward manner.  This RFC822Field is appended to the
     RFC822FieldList, which is added to the IPM Heading as an
     extension field.

     5.1.3.  Generating the IPM

     The IPM (IPMS Service Request) is generated according to the
     rules of this section. The IPMS.IPM.body usually consists of one
     IPMS.BodyPart of type IPMS.IA5TextBodyPart with
     IPMS.IA5TextBodyPart.parameters.repertoire set to the default
     (ia5) which contains the body of the RFC 822 message.  The
     exception is where there is a "Comments:" field in the RFC 822
     header.

          If no specific 1988 features are used, the IPM generated is
     encoded as content type 2.  Otherwise, it is encoded as content
     type 22.  The latter will always be the case if extension heading
     fields are generated.

          When generating the IPM, the issue of upper bounds must be
     considered.  At the MTS and MTA level, this specification is
     strict about enforcing upper bounds. Three options are available
     at the IPM level.  Use of any of these options conforms to this
     standard.

     1.   Ignore upper bounds, and generate messages in the natural
          manner.  This assumes that if any truncation is done, it
          will happen at the recipient UA.  This will maximise
          transfer of information, but is likely break some recipient
          UAs.

     2.   Reject any inbound message which would cause a message
          violating constraints to be generated.  This will be robust,
          but may prevent useful communication.

     3.   Truncate fields to the upper bounds specified in X.400.



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          This will prevent problems with UAs which enforce upper
          bounds, but will sometimes discard useful information.

     These options have different advantages and disadvantages, and
     the choice will depend on the exact application of the gateway.

          The rest of this section concerns IPMS.IPM.heading
     (IPMS.Heading).  The only mandatory component of IPMS.Heading is
     the IPMS.Heading.this-IPM (IPMS.IPMIdentifier).  A default is
     generated by the gateway.  With the exception of "Received:", the
     values of multiple fields are merged (e.g., If there are two
     "To:" fields, then the mailboxes of both are merged to generate a
     single list which is used in the IPMS.Heading.primary-recipients.
     Information shall be generated from the standard RFC 822 Headers
     as follows:

     Date:
          Ignore (Handled at MTS level)

     Received:
          Ignore (Handled at MTA level)

     Message-Id:
          Mapped to IPMS.Heading.this-IPM.  For these, and all other
          fields containing 822.msg-id the mappings of Chapter 4 are
          used for each 822.msg-id.

     From:
          If Sender: is present, this is mapped to
          IPMS.Heading.authorizing-users.  If not, it is mapped to
          IPMS.Heading.originator.  For this, and other components
          containing addresses, the mappings of Chapter 4 are used for
          each address.

     Sender:
          Mapped to IPMS.Heading.originator.

     Reply-To:
          Mapped to IPMS.Heading.reply-recipients.

     To:  Mapped to IPMS.Heading.primary-recipients

     Cc:  Mapped to IPMS.Heading.copy-recipients.




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     Bcc: Mapped to IPMS.Heading.blind-copy-recipients.

     In-Reply-To:
          If there is one value, it is mapped to
          IPMS.Heading.replied-to-IPM, using the 822.phrase or
          822.msg-id mapping as appropriate.  If there are several
          values, they are mapped to IPMS.Heading.related-IPMs, along
          with any values from a "References:" field.

     References:
          Mapped to IPMS.Heading.related-IPMs.

     Keywords:
          Mapped onto a heading extension.

     Subject:
          Mapped to IPMS.Heading.subject.  The field-body uses the
          human oriented mapping referenced in Chapter 3 from ASCII to
          T.61.

     Comments:
          Generate an IPMS.BodyPart of type IPMS.IA5TextBodyPart with
          IPMS.IA5TextBodyPart.parameters.repertoire set to the
          default (ia5), containing the value of the fields, preceded
          by the string "Comments: ".  This body part shall precede
          the other one.

     Encrypted:
          Mapped onto a heading extension.

     Resent-*
          Mapped onto a heading extension.

          Note that it would be possible to use a ForwardedIPMessage
          for these fields, but the semantics are (arguably) slightly
          different, and it is probably not worth the effort.

     Other Fields
          In particular X-* fields, and "illegal" fields in common
          usage (e.g., "Fruit-of-the-day:") are mapped onto a heading
          extension, unless covered by another section or appendix of
          this specification.  The same treatment is applied to RFC
          822 fields where the content of the field does not conform
          to RFC 822 (e.g., a Date: field with unparseable syntax).



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     5.1.4.  Mappings to the MTS Abstract Service

     The MTS.MessageSubmissionEnvelope comprises
     MTS.PerMessageSubmissionFields, and
     MTS.PerRecipientMessageSubmissionFields.  The mandatory
     parameters are defaulted as follows.

     MTS.PerMessageSubmissionFields.originator-name
          This is always generated from 822-MTS, as defined in
          Chapter 4.

     MTS.PerMessageSubmissionFields.content-type
          Set to the value implied by the encoding of the IPM (2 or
          22).

     MTS.PerRecipientMessageSubmissionFields.recipient-name
          These will always be supplied from 822-MTS, as defined in
          Chapter 4.

     Optional components are omitted, and default components
     defaulted, with two exceptions.  For
     MTS.PerMessageSubmissionFields.per-message-indicators, the
     following settings are made:

     -    Alternate recipient is allowed, as it seems desirable to
          maximise the opportunity for (reliable) delivery.

     -    Content return request is set according to the issues
          discussed in Section 5.2.

     MTS.PerMessageSubmissionFields.original-encoded-information-types
     is a set of one element BuiltInEncodedInformationTypes.ia5-text.

     The MTS.PerMessageSubmissionFields.content-correlator is encoded
     as IA5String, and contains the Subject:, Message-ID:, Date:,  and
     To: fields (if present).  This  includes the strings "Subject:",
     "Date:", "To:", "Message-ID:", and appropriate folding.  This
     shall be truncated to MTS.ub-content-correlator-length (512)
     characters.  In addition, if there is a "Subject:" field, the
     MTS.PerMessageSubmissionFields.content-identifier, is set to a
     printable string representation of the contents of it.   If the
     length of this string is greater than MTS.ub-content-id-length
     (16), it should be truncated to 13 characters and the string
     "..." appended. Both are used, due to the much larger upper bound



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     of the content correlator, and that the content id is available
     in X.400(1984).

     5.1.5.  Mappings to the MTA Abstract Service

     There is a need to map directly onto some aspects of the MTA
     Abstract service, for the following reasons:

     -    So the the MTS Message Identifier can be generated from the
          RFC 822 Message-ID:.

     -    So that the submission date can be generated from the
          822.Date.

     -    To prevent loss of trace information

     -    To prevent RFC 822/X.400 looping caused by distribution
          lists or redirects

     The following mappings are defined.

     Message-Id:
          If this is present, the
          MTA.PerMessageTransferFields.message-identifier is generated
          from it, using the mappings described in Chapter 4.

     Date:
          This is used to set the first component of
          MTA.PerMessageTransferFields.trace-information
          (MTA.TraceInformationElement).  The 822-MTS originator is
          mapped into an MTS.ORAddress, and used to derive
          MTA.TraceInformationElement.global-domain-identifier.  The
          optional components of
          MTA.TraceInformationElement.domain-supplied-information are
          omitted, and the mandatory components are set as follows:

            MTA.DomainSuppliedInformation.arrival-time
               This is set to the date derived from Date:

            MTA.DomainSuppliedInformation.routing-action
               Set to relayed.

          The first element of
          MTA.PerMessageTransferFields.internal-trace-information is



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          generated in an analogous manner, although this can be
          dropped later in certain circumstances (see the procedures
          for "Received:").

     Received:
          All RFC 822 trace is used to derive
          MTA.PerMessageTransferFields.trace-information and
          MTA.PerMessageTransferFields.internal-trace-information.
          Processing of Received: lines  follows processing of Date:,
          and is be done from the the bottom to the top of the RFC 822
          header (i.e., in chronological order).  When other trace
          elements are processed (X400-Received: in all cases and Via:
          if Appendix B is supported), the relative ordering shall be
          retained correctly.  The initial element of
          MTA.PerMessageTransferFields.trace-information will be
          generated already (from Date:).

          Consider the Received: field in question.  If the "by"  part
          of the received is present, use it to derive an
          MTS.GlobalDomainIdentifier.  If this is different from the
          one in the last element of
          MTA.PerMessageTransferFields.trace-information
          (MTA.TraceInformationElement.global-domain-identifier)
          create a new MTA.TraceInformationElement, and optionally
          remove
          MTA.PerMessageTransferFields.internal-trace-information.
          This removal shall be done in cases where the message is
          being transferred to another MD where there is no bilateral
          agreement to preserve internal trace beyond the local MD.
          The trace creation is as for internal trace described below,
          except that no MTA field is needed.

          Then add a new element (MTA.InternalTraceInformationElement)
          to MTA.PerMessageTransferFields.internal-trace-information,
          creating this if needed.  This shall be done, even if
          inter-MD trace is created.  The
          MTA.InternalTraceInformationElement.global-domain-identifier
          is set to the value derived.  The
          MTA.InternalTraceInformationElement.mta-supplied-information
          (MTA.MTASuppliedInformation) is set as follows:

            MTA.MTASuppliedInformation.arrival-time
               Derived from the date of the Received: line




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            MTA.MTASuppliedInformation.routing-action
               Set to relayed

          The MTA.InternalTraceInformationElement.mta-name is taken
          from the "by" component of the "Received:" field, truncated
          to MTS.ub-mta-name-length (32).  For example:


             Received: from computer-science.nottingham.ac.uk by
                vs6.Cs.Ucl.AC.UK via Janet with NIFTP  id aa03794;
                28 Mar 89 16:38 GMT

     Generates the string

             vs6.Cs.Ucl.AC.UK


     Note that before transferring the message to some ADMDs,
     additional trace stripping may be required, as the implied path
     through multiple MDs would violate ADMD policy.   This will
     depend on bilateral agreement with the ADMD.

     5.1.6.  Mapping New Fields

     This specification defines a number of new fields for Reports,
     Notifications and IP Messages in Section 5.3.  As this
     specification only aims to preserve existing services, a gateway
     conforming to this specification does not need to map all of
     these fields to X.400.

          Two  extended fields must be mapped, in order to prevent
     looping.  "DL-Expansion-History:" is mapped to
     MTA.PerMessageTransferFields.extensions.dl-expansion-history
     X400-Received: must be mapped to
     MTA.PerMessageTransferFields.trace-information and
     MTA.PerMessageTransferFields.internal-trace-information.

          Some field that shall not be mapped, and should be
     discarded.  The following cannot be mapped back:

     -    Discarded-X400-MTS-Extensions:

     -    Message-Type:




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     -    Discarded-X400-IPMS-Extensions:

          The following may cause problems, due to other information
     not being mapped back (e.g., extension numbers), or due to
     changes made on the RFC 822 side due to list expansion:

     -    X400-Content-Type:

     -    X400-Originator:

     -    X400-Recipients:

     -    X400-MTS-Identifier:

          Other fields may be either discarded or mapped to X.400.  It
     is usually desirable and beneficial to do map, particularly to
     facilitate support of a message traversing multiple gateways.
     These mappings may be onto MTA, MTS, or IPMS services.  The level
     of support for this reverse mapping should be indicated in the
     gateway conformace statement.

     5.2.  Return of Contents

     It is not clear how widely supported the X.400 return of contents
     service will be.  Experience with X.400(1984) suggests that
     support of this service may not be universal.  As this service is
     expected in the RFC 822 world, two approaches are specified.  The
     choice will depend on the use of X.400 return of contents withing
     the X.400 community being serviced by the gateway.

          In environments where return of contents is widely
     supported, content return can be requested as a service.  The
     content return service can then be passed back to the end (RFC
     822) user in a straightforward manner.

          In environments where return of contents is not widely
     supported, a gateway must make special provision to handle return
     of contents.  For every message passing from RFC 822 -> X.400,
     content return request will not be requested, and report request
     always will be.  When the delivery report comes back, the gateway
     can note that the message has been delivered to the recipient(s)
     in question.  If a non-delivery report is received, a meaningful
     report (containing some or all of the original message) can be
     sent to the 822-MTS originator.  If no report is received for a



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     recipient, a (timeout) failure notice shall be sent to the
     822-MTS originator.  The gateway may retransmit the X.400 message
     if it wishes.  When this approach is taken, routing must be set
     up so that error reports are returned through the same MTA.
     This approach may be difficult to use in conjunction with some
     routing strategies.

     5.3.  X.400 -> RFC 822

     5.3.1.  Basic Approach

     A single RFC 822 message is generated from the incoming IP
     Message, Report, or IP Notification.   All IPMS.BodyParts are
     mapped onto a single RFC 822 body.  Other services are mapped
     onto RFC 822 header fields.  Where there is no appropriate
     existing field, new fields are defined for IPMS, MTS and MTA
     services.

          The gateway mechanisms will correspond to MTS Delivery.  As
     with submission, there are aspects where the MTA (transfer)
     services are also used. In particular, there is an optimisation
     to allow for multiple 822-MTS recipients.

     5.3.2.  RFC 822 Settings

     An RFC 822 Service requires to have a number of mandatory fields
     in the RFC 822 Header.  Some 822-MTS services mandate
     specification of an 822-MTS Originator.  Even in cases where this
     is optional, it is usually desirable to specify a value.  The
     following defaults are defined, which shall be used if the
     mappings specified do not derive a value:

     822-MTS Originator
          If this is not generated by the mapping (e.g., for a
          Delivery Report), a value pointing at a gateway
          administrator shall be assigned.

     Date:
          A value will always be generated

     From:If this is not generated by the mapping, it is assigned
          equal to the 822-MTS Originator.  If this is gateway
          generated, an appropriate 822.phrase shall be added.




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     At least one recipient field
          If no recipient fields are generated, a field "To: list:;",
          shall be added.

     This will ensure minimal RFC 822 compliance.  When generating RFC
     822 headers, folding may be used.  It is recommended to do this,
     following the guidelines of RFC 822.

     5.3.3.  Basic Mappings

     5.3.3.1.  Encoded Information Types

     This mapping from MTS.EncodedInformationTypes is needed in
     several disconnected places.  EBNF is defined as follows:

             encoded-info    = 1#encoded-type

             encoded-type    = built-in-eit / object-identifier

             built-in-eit    = "Undefined"         ; undefined (0)
                             / "Telex"             ; tLX (1)
                             / "IA5-Text"          ; iA5Text (2)
                             / "G3-Fax"            ; g3Fax (3)
                             / "TIF0"              ; tIF0 (4)
                             / "Teletex"           ; tTX (5)
                             / "Videotex"          ; videotex (6)
                             / "Voice"             ; voice (7)
                             / "SFD"               ; sFD (8)
                             / "TIF1"              ; tIF1 (9)


     MTS.EncodedInformationTypes is mapped onto EBNF.encoded-info.
     MTS.EncodedInformationTypes.non-basic-parameters is ignored.
     Built in types are mapped onto fixed strings (compatible with
     X.400(1984) and RFC 987), and other types are mapped onto
     EBNF.object-identifier.

     5.3.3.2.  Global Domain Identifier

     The following simple EBNF is used to represent
     MTS.GlobalDomainIdentifier:

             global-id = std-or-address




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     This is encoded using the std-or-address syntax, for the
     attributes within the Global Domain Identifier.

     5.3.4.  Mappings from the IP Message

     Consider that an IPM has to be mapped to RFC 822.  The IPMS.IPM
     comprises an IPMS.IPM.heading and IPMS.IPM.body.   The heading is
     considered first.  Some EBNF for new fields is defined:

             ipms-field = "Obsoletes" ":" 1#msg-id
                        / "Expiry-Date" ":" date-time
                        / "Reply-By" ":" date-time
                        / "Importance" ":" importance
                        / "Sensitivity" ":" sensitivity
                        / "Autoforwarded" ":" boolean
                        / "Incomplete-Copy" ":"
                        / "Language" ":" language
                        / "Message-Type" ":" message-type
                        / "Discarded-X400-IPMS-Extensions" ":" 1#oid



             importance      = "low" / "normal" / "high"


             sensitivity     = "Personal" / "Private" /
                                    "Company-Confidential"

             language        = 2*ALPHA [ language-description ]
             language-description = printable-string



             message-type    = "Delivery Report"
                             / "InterPersonal Notification"
                             / "Multiple Part"

     The mappings and actions for the IPMS.Heading is now specified
     for each element.  Addresses, and Message Identifiers are mapped
     according to Chapter 4.  Other mappings are explained, or are
     straightforward (algorithmic).

     IPMS.Heading.this-IPM
          Mapped to "Message-ID:".



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     IPMS.Heading.originator
          If IPMS.Heading.authorizing-users is present this is mapped
          to Sender:, if not to "From:".

     IPMS.Heading.authorizing-users
          Mapped to "From:".

     IPMS.Heading.primary-recipients
          Mapped to "To:".

     IPMS.Heading.copy-recipients
          Mapped to "Cc:".

     IPMS.Heading.blind-copy-recipients
          Mapped to "Bcc:".

     IPMS.Heading.replied-to-ipm
          Mapped to "In-Reply-To:".

     IPMS.Heading.obsoleted-IPMs
          Mapped to the extended RFC 822 field "Obsoletes:"

     IPMS.Heading.related-IPMs
          Mapped to "References:".

     IPMS.Heading.subject
          Mapped to "Subject:".  The contents are converted to ASCII
          (as defined in Chapter 3).  Any CRLF are not mapped, but are
          used as points at which the subject field must be folded.

     IPMS.Heading.expiry-time
          Mapped to the extended RFC 822 field "Expiry-Date:".

     IPMS.Heading.reply-time
          Mapped to the extended RFC 822 field "Reply-By:".

     IPMS.Heading.reply-recipients
          Mapped to "Reply-To:".

     IPMS.Heading.importance
          Mapped to the extended RFC 822 field "Importance:".

     IPMS.Heading.sensitivity
          Mapped to the extended RFC 822 field "Sensitivity:".



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     IPMS.Heading.autoforwarded
          Mapped to the extended RFC 822 field "Autoforwarded:".

     The standard extensions (Annex H of X.420 / ISO 10021-7) are
     mapped as follows:

     incomplete-copy
          Mapped to the extended RFC 822 field "Incomplete-Copy:".

     language
          Mapped to the extended RFC 822 field "Language:", filling in
          the two letter code. The language-description may filled in
          with a human readable description of the language, and it is
          recommended to do this.

          If the RFC 822 extended header is found, this shall be
     mapped onto an RFC 822 header, as described in Section 5.1.2.

          If a non-standard extension is found, it shall be discarded,
     unless the gateway understands the extension and can perform an
     appropriate mapping onto an RFC 822 header field.  If extensions
     are discarded, the list is indicated in the extended RFC 822
     field "Discarded-X400-IPMS-Extensions:".

          The IPMS.Body is mapped into the RFC 822 message body.  Each
     IPMS.BodyPart is converted to ASCII as follows:

     IPMS.IA5Text
          The mapping is straightforward (see Chapter 3).

     IPMS.MessageBodyPart
          The X.400 -> RFC 822 mapping  is recursively applied, to
          generate an RFC 822 Message.  If present, the
          IPMS.MessageBodyPart.parameters.delivery-envelope is used
          for the MTS Abstract Service Mappings.  If present, the
          IPMS.MessageBodyPart.parameters.delivery-time is mapped to
          the extended RFC 822 field "Delivery-Date:".

     Other
          If other body parts can be mapped to IA5, either by use of
          mappings defined in X.408 [CCITT88a], or by other reasonable
          mappings, this shall be done unless content conversion is
          prohibited.




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          If some or all of the body parts cannot be converted there
     are three options.  All of these conform to this standard.  A
     different choice may be made for the case where no body part can
     be converted:

     1.   The first option is to reject the message, and send a non-
          delivery notification.  This must always be done if
          conversion is prohibited.

     2.   The second option is to map a missing body part to something
          of the style:

                  *********************************

                  There was a foobar here

                  The widget gateway ate it

                  *********************************

          This will allow some useful information to be transferred.
          As the recipient is likely to be a human (IPMS), then
          suitable action will usually be possible.

     3.   Finally both may be done.  In this case, the supplementary
          information in the (positive) Delivery Report shall make
          clear that something was sent on to the recipient with
          substantial loss of information.

          Where there is more than one IPMS.BodyPart, the mapping
     defined by Rose and Stefferud in [Rose85a], is used to map the
     separate IPMS.BodyParts in the single RFC 822 message body.  If
     this is done, a "Message-Type:" field with value "Multiple part"
     shall be added, which will indicate to a receiving gateway that
     the message may be unfolded according to RFC 934.

     Note:There is currently work ongoing to produce an upgrade to RFC
          934, which also allows for support of body parts with non-
          ASCII content.  When this work is released as an RFC, this
          specification will be updated to refer to it instead for RFC
          934.

          For backwards compatibility with RFC 987, the following
     procedures shall also be followed.  If there are two IA5 body



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     parts, and the first starts with the string "RFC-822-Headers:" as
     the first line, then the remainder of this body part shall be
     appended to the RFC 822 header.

          An example message, illustrating a number of aspects is
     given below.

     Return-Path: <@mhs-relay.ac.uk:stephen.harrison@gosip-uk.hmg.gold-400.gb>
     Received: from mhs-relay.ac.uk by bells.cs.ucl.ac.uk via JANET with NIFTP
               id <7906-0@bells.cs.ucl.ac.uk>; Thu, 30 May 1991 18:24:55 +0100
     X400-Received: by mta "mhs-relay.ac.uk" in /PRMD=uk.ac/ADMD= /C=gb/; Relayed;
                    Thu, 30 May 1991 18:23:26 +0100
     X400-Received: by /PRMD=HMG/ADMD=GOLD 400/C=GB/; Relayed;
                    Thu, 30 May 1991 18:20:27 +0100
     Message-Type: Multiple Part
     Date: Thu, 30 May 1991 18:20:27 +0100
     X400-Originator: Stephen.Harrison@gosip-uk.hmg.gold-400.gb
     X400-MTS-Identifier:
          [/PRMD=HMG/ADMD=GOLD 400/C=GB/;PC1000-910530172027-57D8]
     Original-Encoded-Information-Types: ia5, undefined
     X400-Content-Type: P2-1984 (2)
     Content-Identifier: Email Problems
     From: Stephen.Harrison@gosip-uk.hmg.gold-400.gb (Tel +44 71 217 3487)
     Message-ID: <PC1000-910530172027-57D8*@MHS>
     To: Jim Craigie <NTIN36@gec-b.rutherford.ac.uk>
         (Receipt Notification Requested) (Non Receipt Notification Requested),
         Tony Bates <tony@ean-relay.ac.uk> (Receipt Notification Requested),
         Steve Kille <S.Kille@cs.ucl.ac.uk> (Receipt Notification Requested)
     Subject: Email Problems
     Sender: Stephen.Harrison@gosip-uk.hmg.gold-400.gb


     ------------------------------ Start of body part 1

     Hope you gentlemen.......

     Regards,

     Stephen Harrison
     UK GOSIP Project

      ..... continued on next page





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     ------------------------------ Start of forwarded message 1

     From: Urs Eppenberger <Eppenberger@verw.switch.ch>
     Message-ID:
       <562*/S=Eppenberger/OU=verw/O=switch/PRMD=SWITCH/ADMD=ARCOM/C=CH/@MHS>
     To: "Stephen.Harrison" <Stephen.Harrison@gosip-uk.hmg.gold-400.gb>
     Cc: kimura@bsdarc.bsd.fc.nec.co.jp
     Subject: Response to Email link


     - ------------------------------ Start of body part 1

     Dear Mr Harrison......


     - ------------------------------ End of body part 1

     ------------------------------ End of forwarded message 1



     5.3.5.  Mappings from an IP Notification

     A message is generated, with the following fields:

     From:
          Set to the MTS.MessageDeliveryEnvelope.other-
          fields.originator-name.

     To:  Set to the IPMS.IPN.ipm-originator.

     Subject:
          Set to the string  "X.400 Inter-Personal Notification".

     Message-Type:
          Set to "InterPersonal Notification"

     References:
          Set to IPMS.IPN.subject-ipm

     The following EBNF is defined for the body of the Message.  This
     format is defined to ensure that all information from an



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     interpersonal notification is available to the end user in a
     uniform manner.

             ipn-body-format = ipn-description <CRLF>
                             [ ipn-extra-information <CRLF> ]
                             ipn-content-return

             ipn-description = ipn-receipt / ipn-non-receipt

             ipn-receipt = "Your message to:" preferred-recipient <CRLF>
                      "was received at" receipt-time <CRLF> <CRLF>
                      "This notification was generated"
                      acknowledgement-mode <CRLF>
                      "The following extra information was given:" <CRLF>
                      ipn-suppl <CRLF>

             ipn-non-receipt "Your message to:"
                     preferred-recipient <CRLF>
                     ipn-reason


             ipn-reason = ipn-discarded / ipn-auto-forwarded

             ipn-discarded = "was discarded for the following reason:"
                             discard-reason <CRLF>

             ipn-auto-forwarded = "was automatically forwarded." <CRLF>
                             [ "The following comment was made:"
                                     auto-comment ]


             ipn-extra-information =
                      "The following information types were converted:"
                      encoded-info

             ipn-content-return = "The Original Message is not available"
                             / "The Original Message follows:"
                               <CRLF> <CRLF> message


             preferred-recipient = mailbox
             receipt-time        = date-time
             auto-comment        = printablestring
             ipn-suppl           = printablestring



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             discard-reason     = "Expired" / "Obsoleted" /
                                     "User Subscription Terminated"

             acknowledgement-mode = "Manually" / "Automatically"

     The mappings for elements of the common fields of IPMS.IPN
     (IPMS.CommonFields) onto this structure and the message header
     are:

     subject-ipm
          Mapped to "References:"

     ipm-originator
          Mapped  to "To:".

     ipm-preferred-recipient
          Mapped to EBNF.preferred-recipient

     conversion-eits
          Mapped to EBNF.encoded-info in EBNF.ipn-extra-information

     The mappings for elements of IPMS.IPN.non-receipt-fields
     (IPMS.NonReceiptFields) are:

     non-receipt-reason
          Used to select between EBNF.ipn-discarded and
          EBNF.ipn-auto-forwarded

     discard-reason
          Mapped to EBNF.discard-reason

     auto-forward-comment
          Mapped to EBNF.auto-comment

     returned-ipm
          If present, the second option of EBNF.ipn-content-return is
          chosen, and an RFC 822 mapping of the message included.
          Otherwise the first option is chosen.

     The mappings for elements of IPMS.IPN.receipt-fields
     (IPMS.ReceiptFields) are:

     receipt-time



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          Mapped to EBNF.receipt-time

     acknowledgement-mode
          Mapped to EBNF.acknowledgement-mode

     suppl-receipt-info
          Mapped to EBNF.ipn-suppl

     An example notification is:

             From: Steve Kille <steve@cs.ucl.ac.uk>
             To: Julian Onions <jpo@computer-science.nottingham.ac.uk>
             Subject: X.400 Inter-personal Notification
             Message-Type: InterPersonal Notification
             References: <1229.614418325@UK.AC.NOTT.CS>
             Date: Wed, 21 Jun 89 08:45:25 +0100

             Your message to: Steve Kille <steve@cs.ucl.ac.uk>
             was automatically forwarded.
             The following comment was made:
                     Sent on to a random destination

             The following information types were converted: g3fax

             The Original Message is not available



     5.3.6.  Mappings from the MTS Abstract Service

     This section describes the MTS mappings for User Messages (IPM
     and IPN).  This mapping is defined by specifying the mapping of
     MTS.MessageDeliveryEnvelope.  The following extensions to RFC 822
     are defined to support this mapping:













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             mts-field = "X400-MTS-Identifier" ":" mts-msg-id
                       / "X400-Originator" ":" mailbox
                       / "X400-Recipients" ":" 1#mailbox
                       / "Original-Encoded-Information-Types" ":"
                                       encoded-info
                       / "X400-Content-Type" ":" mts-content-type
                       / "Content-Identifier" ":" printablestring
                       / "Priority" ":" priority
                       / "Originator-Return-Address" ":" 1#mailbox
                       / "DL-Expansion-History" ":" mailbox ";" date-time ";"
                       / "Conversion" ":" prohibition
                       / "Conversion-With-Loss" ":" prohibition
                       / "Requested-Delivery-Method" ":"
                                       1*( labelled-integer )
                       / "Delivery-Date" ":" date-time
                       / "Discarded-X400-MTS-Extensions" ":"
                                        1#( oid / labelled-integer )


             prohibition     = "Prohibited" / "Allowed"

             mts-msg-id       = "[" global-id ";" *text "]"

             mts-content-type = "P2" /  labelled-integer
                             / object-identifer

             priority        = "normal" / "non-urgent" / "urgent"


     The mappings for each element of MTS.MessageDeliveryEnvelope can
     now be considered.

     MTS.MessageDeliveryEnvelope.message-delivery-identifier
          Mapped to the extended RFC 822 field "X400-MTS-Identifier:".

     MTS.MessageDeliveryEnvelope.message-delivery-time
          Discarded, as this time will be represented in an
          appropriate trace element.

     The mappings for elements of
     MTS.MessageDeliveryEnvelope.other-fields
     (MTS.OtherMessageDeliveryFields) are:




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     content-type
          Mapped to the extended RFC 822 field "X400-Content-Type:".
          The string "P2" is retained for backwards compatibility with
          RFC 987. This shall not be generated, and either the
          EBNF.labelled-integer  or EBNF.object-identifier encoding
          used.

     originator-name
          Mapped to the 822-MTS originator, and to the extended RFC
          822 field "X400-Originator:".  This is described in
          Section 4.6.2.

     original-encoded-information-types
          Mapped to the extended RFC 822 field
          "Original-Encoded-Information-Types:".

     priority
          Mapped to the extended RFC 822 field "Priority:".

     delivery-flags
          If the conversion-prohibited bit is set, add an extended RFC
          822 field "Conversion:".

     this-recipient-name and other-recipient-names

     originally-intended-recipient-name
          The handling of these elements is described in
          Section 4.6.2.

     converted-encoded-information-types
          Discarded, as it will always be IA5 only.

     message-submission-time
          Mapped to Date:.

     content-identifier
          Mapped to the extended RFC 822 field "Content-Identifier:".

     If any extensions
     (MTS.MessageDeliveryEnvelope.other-fields.extensions) are
     present, and they are marked as critical for transfer or
     delivery, then the message shall be rejected.  The extensions
     (MTS.MessageDeliveryEnvelope.other-fields.extensions) are mapped
     as follows.



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     conversion-with-loss-prohibited
          If set to
          MTS.ConversionWithLossProhibited.conversion-with-loss-prohibited,
          then add the extended RFC 822 field "Conversion-With-Loss:".

     requested-delivery-method
          Mapped to the extended RFC 822 field
          "Requested-Delivery-Method:".

     originator-return-address
          Mapped to the extended RFC 822 field
          "Originator-Return-Address:".

     physical-forwarding-address-request
     physical-delivery-modes
     registered-mail-type
     recipient-number-for-advice
     physical-rendition-attributes
     physical-delivery-report-request
     physical-forwarding-prohibited


          These elements are only appropriate for physical delivery.
          They are represented as comments in the "X400-Recipients:"
          field, as described in Section 4.6.2.2.

     originator-certificate
     message-token
     content-confidentiality-algorithm-identifier
     content-integrity-check
     message-origin-authentication-check
     message-security-label
     proof-of-delivery-request

          These elements imply use of security services not available
          in the RFC 822 environment.  If they are marked as critical
          for transfer or delivery, then the message shall be
          rejected.  Otherwise they are discarded.

     redirection-history
          This is described in Section 4.6.2.

     dl-expansion-history
          Each element is mapped to the extended RFC 822 field



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          "DL-Expansion-History:".  They shall be ordered in the
          message header, so that the most recent expansion comes
          first (same order as trace).

          If any MTS (or MTA) Extensions not specified in X.400 are
     present, and they are marked as critical for transfer or
     delivery, then the message shall be rejected.  If they are not so
     marked, they can safely be discarded.  The list of discarded
     fields shall be indicated in the extended header
     "Discarded-X400-MTS-Extensions:".

     5.3.7.  Mappings from the MTA Abstract Service

     There are some mappings at the MTA Abstract Service level which
     are done for IPM and IPN.  These can be derived from
     MTA.MessageTransferEnvelope.  The reasons for the mappings at
     this level, and the violation of layering are:

     -    Allowing for multiple recipients to share a single RFC 822
          message

     -    Making the X.400 trace information available on the RFC 822
          side

     -    Making any information on deferred delivery available

     The 822-MTS recipients are calculated from the full list of X.400
     recipients.  This is all of the members of
     MTA.MessageTransferEnvelope.per-recipient-fields being passed
     through the gateway, where the responsibility bit is set.  In
     some cases, a different RFC 822 message would be calculated for
     each recipient, due to differing service requests for each
     recipient.  As discussed in 4.6.2..2, this specification allows
     either for multiple messages to be generated, or for the per-
     recipient information to be discarded.

     The following EBNF is defined for extended RFC 822 headers:


             mta-field       = "X400-Received" ":" x400-trace
                             / "Deferred-Delivery" ":" date-time
                             / "Latest-Delivery-Time" ":" date-time





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             x400-trace       = "by" md-and-mta ";"
                              [ "deferred until" date-time ";" ]
                              [ "converted" "(" encoded-info ")" ";" ]
                              [ "attempted" md-or-mta ";"  ]
                                 action-list
                                 ";" arrival-time


             md-and-mta       = [ "mta" mta "in" ]  global-id
             mta              = word
             arrival-time     = date-time

             md-or-mta        = "MD" global-id
                              / "MTA" mta

             Action-list      = 1#action
             action           = "Redirected"
                              / "Expanded"
                              / "Relayed"
                              / "Rerouted"




          Note the EBNF.mta is encoded as 822.word.  If the character
     set does no allow encoding as 822.atom, the 822.quoted-string
     encoding is used.

          If MTA.PerMessageTransferFields.deferred-delivery-time is
     present, it is used to generate a Deferred-Delivery: field.  For
     some reason, X.400 does not make this information available at
     the MTS level on delivery.  X.400 profiles, and in particular the
     CEN/CENELEC profile for X.400(1984) [Systems85a], specify that
     this element must be supported at the first MTA.  If it is not,
     the function may optionally be implemented by the gateway: that
     is, the gateway may hold the message until the time specified in
     the protocol element.  Thus, the value of this element will
     usually be in the past.  For this reason, the extended RFC 822
     field is primarily for information.

          Merge MTA.PerMessageTransferFields.trace-information, and
     MTA.PerMessageTransferFields.internal-trace-information to



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     produce a single ordered trace list.  If Internal trace from
     other management domains has not been stripped, this may require
     complex interleaving. Where an element of internal trace and
     external trace are identical, except for the MTA in the internal
     trace, only the internal trace element shall be presented. Use
     this to generate a sequence of "X400-Received:" fields. The only
     difference between external trace and internal trace will be the
     extra MTA information in internal trace elements.

          When generating an RFC 822 message all trace fields (X400-
     Received and Received) shall be at the beginning of the header,
     before any other fields.  Trace shall be in chronological order,
     with the most recent element at the front of the message.  This
     ordering is determined from the order of the fields, not from
     timestamps in the trace, as there is no guarantee of clock
     synchronisation.  A simple example trace (external) is:

     X400-Received: by /PRMD=UK.AC/ADMD=Gold 400/C=GB/ ; Relayed ;
             Tue, 20 Jun 89 19:25:11 +0100

     A more complex example (internal):

     X400-Received: by mta "UK.AC.UCL.CS" in  /PRMD=UK.AC/ADMD=Gold 400/C=GB/ ;
             deferred until  Tue, 20 Jun 89 14:24:22 +0100 ;
             converted (undefined, g3fax) ";" attempted /ADMD=Foo/C=GB/ ;
             Relayed, Expanded, Redirected ; Tue, 20 Jun 89 19:25:11 +0100


     5.3.8.  Mappings from Report Delivery

     Delivery reports are mapped at the MTS service level.  This means
     that only reports destined for the MTS user will be mapped.  Some
     additional services are also taken from the MTA service.

     5.3.8.1.  MTS Mappings

     A Delivery Report service will be represented as
     MTS.ReportDeliveryEnvelope, which comprises of per-report-fields
     (MTS.PerReportDeliveryFields) and per-recipient-fields.

     A message is generated with the following fields:

     From:
          An administrator at the gateway system.  This is also the



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          822-MTS originator.

     To:  A mapping of the
          MTA.ReportTransferEnvelope.report-destination-name.  This is
          also the 822-MTS recipient.

     Message-Type:
          Set to "Delivery Report".

     Subject:
          The EBNF for the subject line is:


             subject-line  = "Delivery-Report" "(" status ")"
                             [ "for" destination ]

             status        = "success" / "failure" / "success and failures"

             destination   = mailbox / "MTA" word


          The format of the body of the message is defined to ensure
     that all information is conveyed to the RFC 822 user in a
     consistent manner.  The format is structured as if it was a
     message coming from X.400, with the description in one body part,
     and a forwarded message (return of content) in the second.  This
     structure is useful to the RFC 822 recipient, as it enables the
     original message to be extracted.  The first body part is
     structured as follows:

     1.   A few lines giving keywords to indicate the original
          message.

     2.   A human summary of the status of each recipient being
          reported on.

     3.   A clearly marked section which contains detailed information
          extracted from the report.  This is marked clearly, as it
          will not be comprehensible to the average user.  It is
          retained, as it may be critical to diagnosing an obscure
          problem.

          This section may be omitted in positive DRs, and it is
          recommended that this is appropriate for most gateways.



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             dr-body-format = dr-summary <CRLF>
                             dr-recipients <CRLF>
                             dr-administrator-info-envelope <CRLF>
                             dr-content-return


             dr-content-return = "The Original Message is not available"
                  / "The Original Message follows:"
                  / "The Orginal Message is not returned with positive reports"

             dr-summary = "This report relates to your message:" <CRLF>
                             content-correlator <CRLF> <CRLF>
                          "of" date-time <CRLF> <CRLF>


             dr-recipients = *(dr-recipient <CRLF> <CRLF>)

             dr-recipient = dr-recip-success / dr-recip-failure

             dr-recip-success =
                             "Your message was successfully delivered to:"
                              mailbox "at" date-time


             dr-recip-failure = "Your message was not delivered to:"
                                     mailbox <CRLF>
                             "for the following reason:" *word


             dr-administrator-info-envelope = 3*( "*" text <CRLF> )


             dr-administrator-info =
              "**** The following information is directed towards"
              "the local administrator" <CRLF>
              "**** and is not intended for the end user" <CRLF> <CRLF>
              "DR generated by:" report-point <CRLF>
              "at" date-time <CRLF> <CRLF>
              "Converted to RFC 822 at" mta <CRLF>
              "at" date-time <CRLF> <CRLF>
              "Delivery Report Contents:" <CRLF> <CRLF>
              drc-field-list <CRLF>
              "***** End of administration information"



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             drc-field-list       = *(drc-field <CRLF>)

             drc-field = "Subject-Submision-Identifier" ":"
                                             mts-msg-id
                       / "Content-Identifier" ":" printablestring
                       / "Content-Type" ":" mts-content-type
                       / "Original-Encoded-Information-Types" ":"
                                     encoded-info
                       / "Originator-and-DL-Expansion-History" ":"
                                     dl-history
                       / "Reporting-DL-Name" ":" mailbox
                       / "Content-Correlator" ":" content-correlator
                       / "Recipient-Info" ":" recipient-info
                       / "Subject-Intermediate-Trace-Information" ":"
                                               x400-trace


             recipient-info  = mailbox "," std-or ";"
                             report-type
                             [ "converted eits" encoded-info ";" ]
                             [ "originally intended recipient"
                                     mailbox "," std-or ";" ]
                             [ "last trace" [ encoded-info ] date-time ";" ]
                             [ "supplementary info" <"> printablestring <"> ";" ]
                             [ "redirection history" 1#redirection ";"
                             [ "physical forwarding address"
                                                   printablestring ";" ]


             report-type     = "SUCCESS" drc-success
                             / "FAILURE" drc-failure

             drc-success     = "delivered at" date-time ";"
                             [ "type of MTS user" labelled-integer ";" ]

             drc-failure     = "reason" labelled-integer ";"
                             [ "diagnostic" labelled-integer ";" ]


             report-point = [ "mta" word "in" ] global-id
             content-correlator = *word
             dl-history = 1#( mailbox "(" date-time ")")




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     The format is defined as a fixed definition of an the outer level
     (EBNF.dr-body-format).  The element
     EBNF.dr-administrator-info-envelope, provides a means of
     encapsulating a section of the header in a manner which is clear
     to the end user.   Each line of this section begins with "*".
     Each element of EBNF.text within
     %EBNF.dr-administrator-info-envelope must not contain <CRLF>.
     This is used to wrap up EBNF.dr-administrator-info, which will
     generate a sequenece of lines not starting with "*".  EBNF.drc-
     fields may be folded using the  RFC 822 folding rules.

          The elements of MTS.ReportDeliveryEnvelope.per-report-fields
     are mapped as follows onto extended RFC 822 fields:

     subject-submission-identifier
          Mapped to EBNF.drc-field (Subject-Submission-Identifier)

     content-identifier
          Mapped to EBNF.drc-field (Content-Identifier).  This should
          also be used in EBNF.dr-summary if there is no Content
          Correlator present.

     content-type
          Mapped to EBNF.drc-field (Content-Type)

     original-encoded-information-types
          Mapped to EBNF.drc-field (Encoded-Info)

     The extensions from
     MTS.ReportDeliveryEnvelope.per-report-fields.extensions are
     mapped as follows:

     originator-and-DL-expansion-history
          Mapped to EBNF.drc-field (Originator-and-DL-Expansion-
          History)

     reporting-DL-name
          Mapped to EBNF.drc-field (Reporting-DL-Name)

     content-correlator
          Mapped to EBNF.content-correlator, provided that the
          encoding is IA5String (this will always be the case).  This
          is used in EBNF.dr-summary and EBNF.drc-field-list.  In the
          former, LWSP may be added, in order to improve the layout of



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          the message.

     message-security-label
     reporting-MTA-certificate
     report-origin-authentication-check

          These security parameters will not be present unless there
          is an error in a remote MTA.  If they are present, they
          shall be discarded in preference to discarding the whole
          report.

     For each element of
     MTS.ReportDeliveryEnvelope.per-recipient-fields, a value of
     EBNF.dr-recipient, and an EBNF.drc-field (Recipient-Info) is
     generated.  The components are mapped as follows.

     actual-recipient-name
          Used to generate the first EBNF.mailbox and EBNF.std-or in
          EBNF.recipient-info.  Both RFC 822 and X.400 forms are
          given, as there may be a problem in the mapping tables.  It
          also generates the EBNF.mailbox in EBNF.dr-recip-success or
          EBNF.dr-recip-failure.

     report
          If it is MTS.Report.delivery, then set EBNF.dr-recipient to
          EBNF.dr-recip-success, and similarly set EBNF.report-type,
          filling in EBNF.drc-success.  If it is a failure, set
          EBNF.dr-recipient to EBNF.dr-recip-failure, making a human
          interpretation of the reason and diagnostic codes, and
          including any supplementary information.  EBNF.drc-failure
          is filled in systematically.

     converted-encoded-information-types
          Set EBNF.drc-field ("converted eits")

     originally-intended-recipient
          Set the second ("originally intended recipient") mailbox and
          std-or in EBNF.drc-field.

     supplementary-info
          Set EBNF.drc-field ("supplementary info"), and include this
          information in EBNF.dr-recip-failure.

     redirection-history



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          Set EBNF.drc-field ("redirection history")

     physical-forwarding-address
          Set ENBF.drc-field ("physical forwarding address")

     recipient-certificate
          Discard

     proof-of-delivery
          Discard

     Any unknown extensions shall be discarded, irrespective of
     criticality.

          The original message, or an extract from it, shall be
     included in the delivery port if it is available.  The original
     message will usually be available at the gateway, as discussed in
     Section 5.2.

     5.3.8.2.  MTA Mappings

          The single 822-MTS recipient is constructed from
     MTA.ReportTransferEnvelope.report-destination-name, using the
     mappings of Chapter 4.  Unlike with a user message, this
     information is not available at the MTS level.

     The following additional mappings are made:

     MTA.ReportTransferEnvelope.report-destination-name
          This is used to generate the To: field.

     MTA.ReportTransferEnvelope.identifier
          Mapped to the extended RFC 822 field "X400-MTS-Identifier:".
          It may also be used to derive a "Message-Id:" field.

     MTA.ReportTransferEnvelope.trace-information
          and

     MTA.ReportTransferEnvelope.internal-trace-information
          Mapped onto the extended RFC 822 field "X400-Received:", as
          described in Section 5.3.7.  The first element is also used
          to generate the "Date:" field, and the EBNF.failure-point.

     MTA.PerRecipientReportTransferFields.last-trace-information



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          Mapped to EBNF.recipient-info (last trace)

     MTA.PerReportTransferFields.subject-intermediate-trace-
          information Mapped to EBNF.drc-field (Subject-Intermediate-
          Trace-Information). These fields are ordered so that the
          most recent trace element comes first.

     5.3.8.3.  Example Delivery Reports

     Example Delivery Report 1:





































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     Return-Path: <postmaster@cs.ucl.ac.uk>
     Received: from cs.ucl.ac.uk by bells.cs.ucl.ac.uk
        via Delivery Reports Channel id <27699-0@bells.cs.ucl.ac.uk>;
        Thu, 7 Feb 1991 15:48:39 +0000
     From: UCL-CS MTA <postmaster@cs.ucl.ac.uk>
     To: S.Kille@cs.ucl.ac.uk
     Subject: Delivery Report (failure) for H.Hildegard@bbn.com
     Message-Type: Delivery Report
     Date: Thu, 7 Feb 1991 15:48:39 +0000
     Message-ID: <"bells.cs.u.694:07.01.91.15.48.34"@cs.ucl.ac.uk>
     Content-Identifier: Greetings.


     ------------------------------ Start of body part 1

     This report relates to your message: Greetings.
             of Thu, 7 Feb 1991 15:48:20 +0000

     Your message was not delivered to
             H.Hildegard@bbn.com for the following reason:
             Bad Address
             MTA 'bbn.com' gives error message  (USER) Unknown user name in
             "H.Hildegard@bbn.com"

     ***** The following information is directed towards the local administrator
     ***** and is not intended for the end user
     *
     * DR generated by mta bells.cs.ucl.ac.uk
     *         in /PRMD=uk.ac/ADMD=gold 400/C=gb/
     *         at Thu, 7 Feb 1991 15:48:34 +0000
     *
     * Converted to RFC 822 at bells.cs.ucl.ac.uk
     *         at Thu, 7 Feb 1991 15:48:40 +0000
     *
      ..... continued on next page











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     * Delivery Report Contents:
     *
     * Subject-Submission-Identifier:
     *          [/PRMD=uk.ac/ADMD=gold 400/C=gb/;<1803.665941698@UK.AC.UCL.CS>]
     * Content-Identifier: Greetings.
     * Subject-Intermediate-Trace-Information:  /PRMD=uk.ac/ADMD=gold 400/C=gb/;
     *          arrival Thu, 7 Feb 1991 15:48:20 +0000 action Relayed

     * Subject-Intermediate-Trace-Information:  /PRMD=uk.ac/ADMD=gold 400/C=gb/;
     *          arrival Thu, 7 Feb 1991 15:48:18 +0000 action Relayed
     * Recipient-Info: H.Hildegard@bbn.com,
     *  /RFC-822=H.Hildegard(a)bbn.com/OU=cs/O=ucl/PRMD=uk.ac/ADMD=gold 400/C=gb/;
     *         FAILURE reason Unable-To-Transfer (1);
     *         diagnostic Unrecognised-ORName (0);
     *         last trace (ia5) Thu, 7 Feb 1991 15:48:18 +0000;
     *         supplementary info "MTA 'bbn.com' gives error message  (USER)
     *         Unknown user name in "H.Hildegard@bbn.com"";
     ****** End of administration information

     The Original Message follows:


     ------------------------------ Start of forwarded message 1

     Received: from glenlivet.cs.ucl.ac.uk by bells.cs.ucl.ac.uk
       with SMTP inbound id <27689-0@bells.cs.ucl.ac.uk>;
       Thu, 7 Feb 1991 15:48:21 +0000
     To: H.Hildegard@bbn.com
     Subject: Greetings.
     Phone: +44-71-380-7294
     Date: Thu, 07 Feb 91 15:48:18 +0000
     Message-ID: <1803.665941698@UK.AC.UCL.CS>
     From: Steve Kille <S.Kille@cs.ucl.ac.uk>


     Steve

     ------------------------------ End of forwarded message 1








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     Example Delivery Report 2:

     Return-Path: <postmaster@cs.ucl.ac.uk>
     Received: from cs.ucl.ac.uk by bells.cs.ucl.ac.uk
       via Delivery Reports Channel id <27718-0@bells.cs.ucl.ac.uk>;
       Thu, 7 Feb 1991 15:49:11 +0000
     X400-Received: by mta bells.cs.ucl.ac.uk in /PRMD=uk.ac/ADMD=gold 400/C=gb/;
       Relayed; Thu, 7 Feb 1991 15:49:08 +0000
     X400-Received: by /PRMD=DGC/ADMD=GOLD 400/C=GB/; Relayed;
       Thu, 7 Feb 1991 15:48:40 +0000
     From: UCL-CS MTA <postmaster@cs.ucl.ac.uk>
     To: S.Kille@cs.ucl.ac.uk
     Subject: Delivery Report (failure) for
              j.nosuchuser@dle.cambridge.DGC.gold-400.gb
     Message-Type: Delivery Report
     Date: Thu, 7 Feb 1991 15:49:11 +0000
     Message-ID: <"DLE/910207154840Z/000"@cs.ucl.ac.uk>
     Content-Identifier: A useful mess...

     This report relates to your message: A useful mess...
     Your message was not delivered to
             j.nosuchuser@dle.cambridge.DGC.gold-400.gb
             for the following reason:
             Bad Address
             DG 21187: (CEO POA) Unknown addressee.

     ***** The following information is directed towards the local administrator
     ***** and is not intended for the end user
     *
      ..... continued on next page
















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     * DR generated by /PRMD=DGC/ADMD=GOLD 400/C=GB/
     *         at Thu, 7 Feb 1991 15:48:40 +0000
     *
     * Converted to RFC 822 at bells.cs.ucl.ac.uk
     *         at Thu, 7 Feb 1991 15:49:12 +0000
     *
     * Delivery Report Contents:
     *
     * Subject-Submission-Identifier:
     *  [/PRMD=uk.ac/ADMD=gold 400/C=gb/;<1796.665941626@UK.AC.UCL.CS>]
     * Content-Identifier: A useful mess...
     * Recipient-Info: j.nosuchuser@dle.cambridge.DGC.gold-400.gb,
     *         /I=j/S=nosuchuser/OU=dle/O=cambridge/PRMD=DGC/ADMD=GOLD 400/C=GB/;
     *         FAILURE reason Unable-To-Transfer (1);
     *         diagnostic Unrecognised-ORName (0);
     *         supplementary info "DG 21187: (CEO POA) Unknown addressee.";
     ****** End of administration information

     The Original Message is not available



     5.3.9.  Probe

     This is an MTS internal issue.  Any probe shall be serviced by
     the gateway, as there is no equivalent RFC 822 functionality.
     The value of the reply is dependent on whether the gateway could
     service an MTS Message with the values specified in the probe.
     The reply shall make use of MTS.SupplementaryInformation to
     indicate that the probe was serviced by the gateway.
















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     Appendix A - Mappings Specific to SMTP

     This Appendix is specific to the Simple Mail Transfer  Protocol
     (RFC 821).  It describes specific changes in the context of this
     protocol.  When servicing a probe, as described in section 5.3.9,
     use may be made of the SMTP VRFY command to increase the accuracy
     of information contained in the delivery report.








































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     Appendix B - Mappings specific to the JNT Mail

          This Appendix is specific to the JNT Mail Protocol.  It
          describes specific changes in the context of this
          protocol.


     1.  Introduction

     There are five aspects of a gateway which are JNT Mail Specific.
     These are each given a section of this appendix.

     2.  Domain Ordering

     When interpreting and generating domains, the UK NRS domain
     ordering shall be used, both in headers, and in text generated
     for human description.

     3.  Addressing

     A gateway which maps to JNT Mail should recognise the Domain
     Defined Attribute JNT-MAIL.  The value associated with this
     attribute should be interpreted according to the JNT Mail
     Specification.  This DDA shall never be generated by a gateway.
     For this reason, the overflow mechanism is not required.

     4.  Acknowledge-To:

     This field has no direct functional equivalent in X.400.
     However, it can be supported to an extent, and can be used to
     improve X.400 support.

          If an Acknowledge-To: field is present when going from JNT
     Mail to X.400, there are two different situations.  The first
     case is where there is one address in the Acknowledge-To: field,
     and it is equal to the 822-MTS return address.   In this case,
     the
     MTS.PerRecipientSubmissionFields.originator-request-report.report
     shall be set for each recipient, and the Acknowledge-To: field
     discarded.  Here, X.400 can provide the equivalent service.

          In all other cases two actions are taken.

     1.   Acknowledgement(s) may be generated by the gateway.  The



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          text of these acknowledgements shall indicate that they are
          generated by the gateway, and do not correspond to delivery.

     2.   The Acknowledge-To: field shall be passed as an extension
          heading.

          When going from X.400 to JNT Mail, in cases where
     MTA.PerRecipientMessageTransferFields.per-recipient-indicators.
     originator-report bit is set for all recipients (i.e., there is a
     user request for a positive delivery report for every recipeint),
     generate an Acknowledge-To: field containing the
     MTS.OtherMessageDeliveryFields.originator-name.  Receipt
     notification requests are not mapped onto Acknowledge-To:, as no
     association can be guaranteed between IPMS and MTS level
     addressing information.

     5.  Trace

     JNT Mail trace uses the Via: syntax.  When going from JNT Mail to
     X.400, a mapping similar to that for Received:  is used. No
     MTS.GlobalDomainIdentifier of the site making the trace can be
     derived from the Via:, so a value for the gateway is used.  The
     trace text, including the "Via:", is unfolded, truncated to
     MTS.ub-mta-name-length (32), and mapped to
     MTA.InternalTraceInformationElement.mta-name.  There is no JNT
     Mail specific mapping for the reverse direction.

     6.  Timezone specification

     The extended syntax of zone defined in the JNT Mail Protocol
     shall be used in the mapping of UTCTime defined in Chapter 3.

     7.  Lack of 822-MTS originator specification

     In JNT Mail the default mapping of the
     MTS.OtherMessageDeliveryFields.originator-name is to the Sender:
     field.  This can cause a problem when going from X.400 to JNT
     Mail if the mapping of IPMS.Heading has already generated a
     Sender: field.  To overcome this, new extended JNT Mail field is
     defined.  This is chosen to align with the JNT recommendation for
     interworking with full RFC 822 systems [Kille84b].

             original-sender     = "Original-Sender" ":" mailbox




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     If an IPM has no IPMS.Heading.authorizing-users component and
     IPMS.Heading.originator.formal-name is different from
     MTS.OtherMessageDeliveryFields.originator-name, map
     MTS.OtherMessageDeliveryFields.originator-name, onto the Sender:
     field.

     If an IPM has a IPMS.Heading.authorizing-users component, and
     IPMS.Heading.originator.formal-name is different from
     MTS.OtherMessageDeliveryFields.originator-name,
     MTS.OtherMessageDeliveryFields.originator-name is mapped onto the
     Sender: field, and IPMS.Heading.originator mapped onto the
     Original-Sender: field.

     In other cases the
     MTS.OtherMessageDeliveryFields.originator-name, is already
     correctly represented.































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     Appendix C - Mappings specific to UUCP Mail


     Gatewaying of UUCP and X.400 is handled by first gatewaying
     the UUCP address into RFC 822 syntax (using RFC 976) and
     then gatewaying the resulting RFC 822 address into X.400.
     For example, an X.400 address

             Country         US
             Organisation    Xerox
             Personal Name   John Smith

     might be expressed from UUCP as

             inthop!gate!gatehost.COM!/C=US/O=Xerox/PN=John.Smith/

     (assuming gate is a UUCP-ARPA gateway and gatehost.COM is an
     ARPA-X.400 gateway) or

             inthop!gate!Xerox.COM!John.Smith

     (assuming that Xerox.COM and /C=US/O=Xerox/ are equivalent.)

     In the other direction, a UUCP address Smith@ATT.COM, integrated
     into 822, would be handled as any other 822 address.  A non-integrated
     address such as inthop!dest!user might be handled through a pair of
     gateways:

             Country         US
             ADMD            ATT
             PRMD            ARPA
             Organisation    GateOrg
             RFC-822         inthop!dest!user@gatehost.COM

     or through a single X.400 to UUCP gateway:


             Country         US
             ADMD            ATT
             PRMD            UUCP
             Organisation    GateOrg
             RFC-822         inthop!dest!user





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     Appendix D - Object Identifier Assignment


     An object identifier is needed for the extension IPMS element.
     The following value shall be used.


     rfc-987-88 OBJECT IDENTIFIER ::=
         {ccitt data(9) pss(2342) ucl(234219200300) rfc-987-88(200)}

     id-rfc-822-field-list OBJECT IDENTIFIER ::= {rfc987-88 field(1)}




































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     Appendix E - BNF Summary



             boolean = "TRUE" / "FALSE"


             numericstring = *DIGIT


             printablestring  = *( ps-char )
             ps-restricted-char      = 1DIGIT /  1ALPHA / " " / "'" / "+"
                                / "," / "-" / "." / "/" / ":" / "=" / "?"
             ps-delim         = "(" / ")"
             ps-char          = ps-delim / ps-restricted-char


             ps-encoded       = *( ps-restricted-char / ps-encoded-char )
             ps-encoded-char  = "(a)"               ; (@)
                              / "(p)"               ; (%)
                              / "(b)"               ; (!)
                              / "(q)"               ; (")
                              / "(u)"               ; (_)
                              / "(l)"               ; "("
                              / "(r)"               ; ")"
                              / "(" 3DIGIT ")"


             teletex-string   = *( ps-char / t61-encoded )
             t61-encoded      = "{" 1* t61-encoded-char "}"
             t61-encoded-char = 3DIGIT


             teletex-and-or-ps = [ printablestring ] [ "*" teletex-string ]


             labelled-integer ::= [ key-string ] "(" numericstring ")"

             key-string      = *key-char
             key-char        = <a-z, A-Z, 0-9, and "-">







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             object-identifier  ::= oid-comp object-identifier
                             | oid-comp

             oid-comp ::= [ key-string ] "(" numericstring ")"


             encoded-info    = 1#encoded-type

             encoded-type    = built-in-eit / object-identifier

             built-in-eit    = "Undefined"         ; undefined (0)
                             / "Telex"             ; tLX (1)
                             / "IA5-Text"          ; iA5Text (2)
                             / "G3-Fax"            ; g3Fax (3)
                             / "TIF0"              ; tIF0 (4)
                             / "Teletex"           ; tTX (5)
                             / "Videotex"          ; videotex (6)
                             / "Voice"             ; voice (7)
                             / "SFD"               ; sFD (8)
                             / "TIF1"              ; tIF1 (9)



             encoded-pn      = [ given "." ] *( initial "." ) surname

             given           = 2*<ps-char not including ".">

             initial         = ALPHA

             surname         = printablestring
















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             std-or-address  = 1*( "/" attribute "=" value ) "/"
             attribute       = standard-type
                             / "RFC-822"
                             / registered-dd-type
                             / dd-key "." std-printablestring
             standard-type   = key-string

             registered-dd-type
                             = key-string
             dd-key          = key-string

             value           = std-printablestring

             std-printablestring
                             = *( std-char / std-pair )
             std-char        = <"{", "}", "*", and any ps-char
                                             except "/" and "=">
             std-pair        = "$" ps-char


             dmn-or-address  = dmn-part *( "." dmn-part )
             dmn-part        = attribute "$" value
             attribute       = standard-type
                             / "~" dmn-printablestring
             value           = dmn-printablestring
                             / "@"
             dmn-printablestring =
                             = *( dmn-char / dmn-pair )
             dmn-char        = <"{", "}", "*", and any ps-char
                                                     except ".">
             dmn-pair        = "\."


             global-id = std-or-address



             mta-field       = "X400-Received" ":" x400-trace
                             / "Deferred-Delivery" ":" date-time
                             / "Latest-Delivery-Time" ":" date-time






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             x400-trace       = "by" md-and-mta ";"
                              [ "deferred until" date-time ";" ]
                              [ "converted" "(" encoded-info ")" ";" ]
                              [ "attempted" md-or-mta ";"  ]
                                 action-list
                                 ";" arrival-time


             md-and-mta       = [ "mta" mta "in" ]  global-id
             mta              = word
             arrival-time     = date-time

             md-or-mta        = "MD" global-id
                              / "MTA" mta

             Action-list      = 1#action
             action           = "Redirected"
                              / "Expanded"
                              / "Relayed"
                              / "Rerouted"

























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             dr-body-format = dr-summary <CRLF>
                             dr-recipients <CRLF>
                             dr-administrator-info-envelope <CRLF>
                             dr-content-return


             dr-content-return = "The Original Message is not available"
                  / "The Original Message follows:"
                  / "The Orginal Message is not returned with positive reports"

             dr-summary = "This report relates to your message:" <CRLF>
                             content-correlator <CRLF> <CRLF>
                          "of" date-time <CRLF> <CRLF>


             dr-recipients = *(dr-recipient <CRLF> <CRLF>)

             dr-recipient = dr-recip-success / dr-recip-failure

             dr-recip-success =
                             "Your message was successfully delivered to:"
                              mailbox "at" date-time


             dr-recip-failure = "Your message was not delivered to:"
                                     mailbox <CRLF>
                             "for the following reason:" *word


             dr-administrator-info-envelope = 3*( "*" text <CRLF> )


             dr-administrator-info =
              "**** The following information is directed towards"
              "the local administrator" <CRLF>
              "**** and is not intended for the end user" <CRLF> <CRLF>
              "DR generated by:" report-point <CRLF>
              "at" date-time <CRLF> <CRLF>
              "Converted to RFC 822 at" mta <CRLF>
              "at" date-time <CRLF> <CRLF>
              "Delivery Report Contents:" <CRLF> <CRLF>
              drc-field-list <CRLF>
              "***** End of administration information"



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             drc-field-list       = *(drc-field <CRLF>)

             drc-field = "Subject-Submision-Identifier" ":"
                                             mts-msg-id
                       / "Content-Identifier" ":" printablestring
                       / "Content-Type" ":" mts-content-type
                       / "Original-Encoded-Information-Types" ":"
                                     encoded-info
                       / "Originator-and-DL-Expansion-History" ":"
                                     dl-history
                       / "Reporting-DL-Name" ":" mailbox
                       / "Content-Correlator" ":" content-correlator
                       / "Recipient-Info" ":" recipient-info
                       / "Subject-Intermediate-Trace-Information" ":"
                                               x400-trace


             recipient-info  = mailbox "," std-or ";"
                             report-type
                             [ "converted eits" encoded-info ";" ]
                             [ "originally intended recipient"
                                     mailbox "," std-or ";" ]
                             [ "last trace" [ encoded-info ] date-time ";" ]
                             [ "supplementary info" <"> printablestring <"> ";" ]
                             [ "redirection history" 1#redirection ";"
                             [ "physical forwarding address"
                                                   printablestring ";" ]


             report-type     = "SUCCESS" drc-success
                             / "FAILURE" drc-failure

             drc-success     = "delivered at" date-time ";"
                             [ "type of MTS user" labelled-integer ";" ]

             drc-failure     = "reason" labelled-integer ";"
                             [ "diagnostic" labelled-integer ";" ]


             report-point = [ "mta" word "in" ] global-id
             content-correlator = *word
             dl-history = 1#( mailbox "(" date-time ")")




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             mts-field = "X400-MTS-Identifier" ":" mts-msg-id
                       / "X400-Originator" ":" mailbox
                       / "X400-Recipients" ":" 1#mailbox
                       / "Original-Encoded-Information-Types" ":"
                                       encoded-info
                       / "X400-Content-Type" ":" mts-content-type
                       / "Content-Identifier" ":" printablestring
                       / "Priority" ":" priority
                       / "Originator-Return-Address" ":" 1#mailbox
                       / "DL-Expansion-History" ":" mailbox ";" date-time ";"
                       / "Conversion" ":" prohibition
                       / "Conversion-With-Loss" ":" prohibition
                       / "Requested-Delivery-Method" ":"
                                       1*( labelled-integer )
                       / "Delivery-Date" ":" date-time
                       / "Discarded-X400-MTS-Extensions" ":"
                                        1#( oid / labelled-integer )


             prohibition     = "Prohibited" / "Allowed"

             mts-msg-id       = "[" global-id ";" *text "]"

             mts-content-type = "P2" /  labelled-integer
                             / object-identifer

             priority        = "normal" / "non-urgent" / "urgent"



















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             ipn-body-format = ipn-description <CRLF>
                             [ ipn-extra-information <CRLF> ]
                             ipn-content-return

             ipn-description = ipn-receipt / ipn-non-receipt

             ipn-receipt = "Your message to:" preferred-recipient <CRLF>
                      "was received at" receipt-time <CRLF> <CRLF>
                      "This notification was generated"
                      acknowledgement-mode <CRLF>
                      "The following extra information was given:" <CRLF>
                      ipn-suppl <CRLF>

             ipn-non-receipt "Your message to:"
                     preferred-recipient <CRLF>
                     ipn-reason


             ipn-reason = ipn-discarded / ipn-auto-forwarded

             ipn-discarded = "was discarded for the following reason:"
                             discard-reason <CRLF>

             ipn-auto-forwarded = "was automatically forwarded." <CRLF>
                             [ "The following comment was made:"
                                     auto-comment ]


             ipn-extra-information =
                      "The following information types were converted:"
                      encoded-info

             ipn-content-return = "The Original Message is not available"
                             / "The Original Message follows:"
                               <CRLF> <CRLF> message


             preferred-recipient = mailbox
             receipt-time        = date-time
             auto-comment        = printablestring
             ipn-suppl           = printablestring





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             discard-reason     = "Expired" / "Obsoleted" /
                                     "User Subscription Terminated"

             acknowledgement-mode = "Manually" / "Automatically"


             ipms-field = "Obsoletes" ":" 1#msg-id
                        / "Expiry-Date" ":" date-time
                        / "Reply-By" ":" date-time
                        / "Importance" ":" importance
                        / "Sensitivity" ":" sensitivity
                        / "Autoforwarded" ":" boolean
                        / "Incomplete-Copy" ":"
                        / "Language" ":" language
                        / "Message-Type" ":" message-type
                        / "Discarded-X400-IPMS-Extensions" ":" 1#oid



             importance      = "low" / "normal" / "high"


             sensitivity     = "Personal" / "Private" /
                                    "Company-Confidential"

             language        = 2*ALPHA [ language-description ]
             language-description = printable-string



             message-type    = "Delivery Report"
                             / "InterPersonal Notification"
                             / "Multiple Part"













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             redirect-comment  =
                      [ "Originally To:" ] mailbox "Redirected"
                      [ "Again" ] "on" date-time
                      "To:"  redirection-reason

             redirection-reason =
                      "Recipient Assigned Alternate Recipient"
                      / "Originator Requested Alternate Recipient"
                      / "Recipient MD Assigned Alternate Recipient"


             subject-line  = "Delivery-Report" "(" status ")"
                             [ "for" destination ]

             status        = "success" / "failure" / "success and failures"

             destination   = mailbox / "MTA" word


             extended-heading =
                 "Prevent-NonDelivery-Report" ":"
                 / "Generate-Delivery-Report" ":"
                 / "Alternate-Recipient" ":" prohibition
                 / "Disclose-Recipients" ":"  prohibition
                 / "Content-Return" ":" prohibition





















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     Appendix F - Format of address mapping tables



     1.  Global Mapping Information

     The consistent operation of gateways which follow this
     specification relies of the existence of three globally defined
     mappings:

     1.   Domain Name Space -> O/R Address Space

     2.   O/R Address Space -> Domain Name Space

     3.   Domain Name Space -> O/R Address of preferred gateway

     All gateways conforming to this specification shall have access
     to these mappings.  The gateway may use standardised or private
     mechanisms to access this mapping information.

          One means of distributing this information is in three
     files.  This appendix defines a format for these files.  Other
     standardised mechanisms to distribute the mapping information are
     expected.  In particular, mechanisms for using the Domain Name
     Scheme, and X.500 are planned.

          The definition of  global mapping information is being co-
     ordinated by the COSINE-MHS project, on behalf of the Internet
     and other X.400 and RFC 822 users.  For information on accessing
     this information contact:
          COSINE MHS Project Team
          SWITCH
          Weinburgstrasse 18
          8001 Zuerich
          Switzerland

          tel: +41 1 262 3143
          fax: +41 1 262 3151
          email:
          C=ch;ADMD=arcom;PRMD=switch;O=switch;OU=cosine-mhs;S=project-team
          or
          project-team@cosine-mhs.switch.ch





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     2.  Syntax Definitions

     An address syntax is defined, which is compatible with the syntax
     used for 822.domains.  By representing the O/R addresses as
     domains, all lookups can be mechanically implemented as domain ->
     domain mappings.  This syntax defined is initially for use in
     table format, but the syntax is defined in a manner which makes
     it suitable to be adapted for  use with the  Domain Name Service.
     This syntax allows for a general representation of O/R addresses,
     so that it can be used in other applications.  Not all attributes
     are used in the table formats defined.

          To allow the mapping of null attributes  to be represented,
     the pseudo-value "@" (not a printable string character) is used
     to indicate omission of a level in the hierarchy.  This is
     distinct from the form including the element with no value,
     although a correct X.400 implementation will interpret both in
     the same manner.

     This syntax is not intended to be handled by users.

             dmn-or-address  = dmn-part *( "." dmn-part )
             dmn-part        = attribute "$" value
             attribute       = standard-type
                             / "~" dmn-printablestring
             value           = dmn-printablestring
                             / "@"
             dmn-printablestring =
                             = *( dmn-char / dmn-pair )
             dmn-char        = <"{", "}", "*", and any ps-char
                                                     except ".">
             dmn-pair        = "\."

     An example usage:

             ~ROLE$Big\.Chief.ADMD$ATT.C$US
             PRMD$DEC.ADMD$@.C$US

     The first example illustrates quoting of a ".", and the second
     omission of the ADMD level. There must be a strict ordering of
     all components in this table, with the most significant
     components on the RHS.   This allows the encoding to be treated
     as a domain.




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          Various further restrictions are placed on the usage of
     dmn-or-address in the address space mapping tables.

     1.   Only C, ADMD, PRMD, O, and up to four OUs may be used.

     2.   No components shall be omitted from this hierarchy, although
          the hierarchy may terminate at any level.  If the mapping is
          to an omitted component, the "@" syntax is used.

     3.  Table Lookups

     When determining a match, there are aspects which apply to all
     lookups.  Matches are always case independent. The key for all
     three  tables is a domain. The longest possible match shall be
     obtained.  Suppose the table has two entries with the following
     keys:

             K.L
             J.K.L

     Domain "A.B.C" will not return any matches.  Domain "I.J.K.L"
     will match the entry "J.K.L:.

     4.  Domain -> O/R Address format

     The BNF is:

             domain-syntax "#" dmn-or-address "#"

     Note that the trailing "#" is used for clarity, as the dmn-or-
     address syntax might lead to values with trailing blanks.  Lines
     staring with "#" are comments.

             For example:
             AC.UK#PRMD$UK\.AC.ADMD$GOLD 400.C$GB#
             XEROX.COM#O$Xerox.ADMD$ATT.C$US#
             GMD.DE#O$@.PRMD$GMD.ADMD$DBP.C$DE#

     A domain is looked up to determine the top levels of an O/R
     Address.  Components of the domain which are not matched are used
     to build the remainder of the O/R address, as described in
     Section 4.3.4.





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     5.  O/R Address -> Domain format

     The syntax of this table is:

             dmn-or-address "#" domain-syntax "#"


             For example:

             #
             # Mapping table
             #
             PRMD$UK\.AC.ADMD$GOLD 400.C$GB#AC.UK#

     The O/R Address is used to generate a domain key.  It is
     important to order the components correctly, and to fill in
     missing components in the hierarchy.  Use of this mapping is
     described in Section 4.3.2.

     6.  Domain -> O/R Address of Gateway table

     This uses the same format as the domain -> O/R address mapping.
     In this case, the two restrictions (omitted components and
     restrictions on components) do not apply.  Use of this mapping is
     described in Section 4.3.4.






















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     Appendix G - Mapping with X.400(1984)


     This appendix defines modification to the  mapping for use with
     X.400(1984).

          The X.400(1984) protocols are a proper subset of
     X.400(1988).  When mapping from X.400(1984) to RFC 822, no
     changes to this specification are needed.

          When mapping from RFC 822 to X.400(1984), no use can be made
     of 1988 specific features.   No use of such features is made at
     the MTS level.  One feature is used at the IPMS level, and this
     must be replaced by the RFC 987 approach.  All header information
     which would usually be mapped into the rfc-822-heading-list
     extension, together with any Comments: field in the RFC 822
     header is mapped into a single IA5 body part, which is the first
     body part in the message.  This body part will start with the
     string "RFC-822-Headers:" as the first line.  The headers then
     follow this line.  This specification requires correct reverse
     mapping of this format, either from 1988 or 1984.

          In an environment where RFC 822 is of major importance, it
     may be desirable for downgrading to consider the case where the
     message was originated in an RFC 822 system, and mapped according
     to this specification.  The rfc-822-heading-list extension may be
     mapped according to this appendix.

          When parsing std-or, the following restrictions must be
     observed:

     -    Only the 84/88 attributes identified in the table in
          Section 4.2 are present.

     -    No teletex encoding is allowed.

     If an address violates this, it should be treated as an RFC 822
     address, which will usually lead to encoding as a DDA "RFC-822".

          It is possible that null attributes may be present in an O/R
     Address.  This is not legal in 1988, except for ADMD where the
     case is explicitly described in Section 4.3.5.  Null attributes
     are deprecated (the attribute should be omitted), and should
     therefore be unusual.  However, some systems generate them and



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     rely on them.  Therefore, any null attribute shall be enoded
     using the std-or encoding (e.g., /O=/).

          If a non-Teletex Common Name (CN) is present, it should be
     mapped onto a Domain Defined Attribute "Common".  This is in line
     with RFC XXXX on X.400 1988 to 1984 downgrading [Hardcastle-
     K91a].








































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     Appendix H - RFC 822 Extensions for X.400 access

     This appendix defines a number of optional mappings which may be
     provided to give access from RFC 822 to a number of X.400
     services.  These mappings are beyond the basic scope of this
     specification.  There has been a definite demand to use extended
     RFC 822 as a mechanism to acccess X.400, and these extensions
     provide access to certain features.  If this functionality is
     provided, this appendix shall be followed.  The following
     headings are defined:

             extended-heading =
                 "Prevent-NonDelivery-Report" ":"
                 / "Generate-Delivery-Report" ":"
                 / "Alternate-Recipient" ":" prohibition
                 / "Disclose-Recipients" ":"  prohibition
                 / "Content-Return" ":" prohibition



     Prevent-NonDelivery-Report and Generate-Delivery-Report allow
     setting of
     MTS.PerRecipientSubmissionFields.originator-report-request.  The
     setting will be the same for all recipients.

          Alternate-Recipient, Disclose-Recipients, and Content-Return
     allow for override of the default settings for
     MTS.PerMessageIndicators.



















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     Appendix I - Conformance


     This appendix defines a number of options, which a conforming
     gateway should specify.  Conformance to this specification shall
     not be claimed if any of the mandatory features are not
     implemented.  In particular:

     -    Formats for all fields shall be followed.

     -    Formats for subject lines, delivery reports and IPNs shall
          be followed.   A system which followed the syntax, but
          translated text into a language other than english would be
          conformant.

     -    RFC 1137 shall not be followed when mapping to SMTP or to
          JNT Mail

     -    All mappings of trace shall be implemented.

     -    There must be a mechanism to access all three global
          mappings.

     A gateway should specify:

     -    Which 822-MTS protocols are supported.  The relevant
          appendices must be followed to claim support of a given
          protocol: SMTP (A); JNT Mail (B); UUCP (C).

     -    The means by which it can access the global mappings.
          Currently, the tables of the formats define in  Appendix F
          is the only means available.

     -    The approach taken when upper bounds are exceeded at the IPM
          level  (5.1.3)

     -    The approach taken to return of contents (5.2)

     -    The approach taken to body parts which cannot be converted
          (5.3.4)

     -    The approach taken to multiple copies vs non-disclosure
          (4.6.2.2)




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     The following are optional parts of this specification.  A
     conforming implementation should specify which of these it
     supports.

     -    Support of X.400(1984), following Appendix G.

     -    Generation of extended RFC 822 fields is mandatory.
          Optionally, they may be parsed and mapped back to X.400.  A
          gateway should should indicate if this is done.

     -    Support for the extension mappings of Appendix H.

     -    Support for the ordered OU mappings (OU1 etc.).

     -    Which address interpretation heuristics are supported
          (4.3.4.1)

     -    If RFC 987 generated message ids are handled in a backwards
          compatible manner (4.7.3.6)




























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          Appendix J - Change History: RFC 987, 1026, 1138, 1148


     RFC 987 was the original document, and contained the key elements
     of this specification.  It was specific to X.400(1984).  RFC 1026
     specified a small number of necessary changes to RFC 987.

          RFC 1138 was based on the RFC 987 work.  It contained an
     editorial error, and was reissued a few months later as RFC 1148.
     RFC 1148 will be referred to here, as it is the document which is
     widely referred to elsewhere. The major goal of RFC 1148 was to
     upgrade RFC 987 to X.400(1988).  It did this, but did not
     obsolete RFC 987, which was recommended for use with X.400(1984).
     This appendix summarises the changes made in going from RFC 987
     to RFC 1148.

          RFC 1148 noted the following about its upgrade from RFC 987:
     Unnecessary change is usually a bad idea.  Changes on the RFC 822
     side are avoided as far as possible,  so that RFC 822 users do
     not see arbitrary differences between systems conforming to this
     specification, and those following RFC 987.  Changes on the X.400
     side are minimised, but are more  acceptable, due to the mapping
     onto a new set of services and protocols.


     1.  Introduction

     The model has shifted from a protocol based mapping to a service
     based mapping.  This has increased the generality of the
     specification, and improved the model.  This change affects the
     entire document.

          A restriction on scope has been added.

     2.  Service Elements


     -    The new service elements of X.400 are dealt with.

     -    A clear distinction is made between origination and
          reception






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     3.  Basic Mappings


     -    Add teletex support

     -    Add object identifier support

     -    Add labelled integer support

     -    Make PrintableString <-> ASCII mapping reversible

     -    The printable string mapping is aligned to the NBS mapping
          derived from RFC 987.

     4.  Addressing


     -    Support for new addressing attributes

     -    The message ID mapping is changed to not be table driven

     5.  Detailed Mappings


     -    Define extended IPM Header, and use instead of second body
          part for RFC 822 extensions

     -    Realignment of element names

     -    New syntax for reports, simplifying the header and
          introducing a mandatory body format (the RFC 987 header
          format was unusable)

     -    Drop complex autoforwarded mapping

     -    Add full mapping for IP Notifications, defining a body
          format

     -    Adopt an MTS Identifier syntax in line with the O/R Address
          syntax

     -    A new format for X400 Trace representation on the RFC 822
          side




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     6.  Appendices


     -    Move Appendix on restricted 822 mappings to a separate RFC

     -    Delete Phonenet and SMTP Appendixes









































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     Appendix K - Change History: RFC 1148 to this Document



     1.  General


     -    The scope of the document was changed to cover X.400(1984),
          and so obsolete RFC 987.

     -    Changes were made to allow usage to connect RFC 822 networks
          using X.400

     -    Text was tightened to be clear about optional and mandatory
          aspects

     -    A good deal of clarification

     -    A number of minor EBNF errors

     -    Better examples are given

     -    Further X.400 upper bounds are handled correctly

     2.  Basic Mappings


     -    The encoding of object identifier is changed slightly

     3.  Addressing


     -    A global mapping of domain to preferred gateway is
          introduced.

     -    An overflow mechanism is defined for RFC 822 addresses of
          greater than 128 bytes

     -    Changes were made to improve compatability with the PDAM on
          writing O/R Addresses.

     +         The PD and Terminal Type keywords were aligned to the
               PDAM.  It is believed that minimal use has been made of
               the RFC 1148 keywords.



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     +         P and A are allowed as alternate keys for PRMD and ADMD

     +         Where keywords are different, the PDAM keywords are
               alternatives on input.  This is mandatory.

     4.  Detailed Mappings


     -    The format of the Subject: lines is defined.

     -    Illegal use (repetition) of the heading EXTENSION is
          corrected, and a new object identifier assigned.

     -    The Delivery Report format is extensively revised in light
          of operational experience.

     -    The handling of redirects is significantly changed, as the
          previous mechanism did not work.

     5.  Appendices


     -    An SMTP appendix is added, allowing optional use of the VRFY
          command to improve probe information.

     -    Handling of JNT Mail Acknowledge-To is changed slightly.

     -    A DDA JNT-MAIL is allowed on input.

     -    The format definitions of Appendix F are explained further,
          and a third table definition added.

     -    An appendix on use with X.400(1984) is added.

     -    Optional extensions are defined to give RFC 822 access to
          further X.400 facilities.

     -    An appendix on conformance is added.









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          SECURITY CONSIDERATIONS

          Security considerations are not discussed in  this RFC.


          AUTHOR'S ADDRESS

          Steve Kille
          Department of Computer Science
          University College London
          Gower Street
          WC1E 6BT
          England

          Phone: +44-71-380-7294

          EMail: S.Kille@CS.UCL.AC.UK






























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     References


     CCITT88a.
          CCITT, "CCITT Recommendations X.408," Message Handling
          Systems: Encoded Information Type Conversion Rules, December
          1988.

     CCITT/ISO88a.
          CCITT/ISO, "CCITT Recommendations X.400/ ISO IS 10021-1,"
          Message Handling: System and Service Overview , December
          1988.

     CCITT/ISO88b.
          CCITT/ISO, "CCITT Recommendations X.420/ ISO IS 10021-7,"
          Message Handling Systems: Interpersonal Messaging System,
          December 1988.

     CCITT/ISO88c.
          CCITT/ISO, "CCITT Recommendations X.411/ ISO IS 10021-4,"
          Message Handling Systems: Message Transfer System: Abstract
          Service Definition and Procedures, December 1988.

     CCITT/ISO88d.
          CCITT/ISO, "Specification of Abstract Syntax Notation One
          (ASN.1)," CCITT Recommendation X.208 / ISO IS 8824, December
          1988.

     CCITT/ISO91a.
          CCITT/ISO, "Representation of O/R Addresses for Human
          Usage," PDAM to CCITT X.401 / ISO/IEC 10021-2, February
          1991.

     Crocker82a.
          D.H. Crocker, "Standard of the Format of ARPA Internet Text
          Messages," RFC 822, August 1982.

     Hardcastle-K91a.
          S.E. Hardcastle-Kille, "X.400 1988 to 1984 downgrading," RFC
          XXXXX, August 1991.

     Horton86a.
          M.R. Horton, "UUCP Mail Interchange Format Standard," RFC
          976, February 1986.



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     Kille84b.
          S.E. Kille, "Gatewaying between RFC 822 and JNT Mail," JNT
          Mailgroup Note 15, May 1984.

     Kille84a.
          S.E. Kille (Editor), JNT Mail Protocol (revision 1.0), Joint
          Network Team, Rutherford Appleton Laboratory, March 1984.

     Kille86a.
          S.E. Kille, "Mapping Between X.400 and RFC 822," UK Academic
          Community Report (MG.19) / RFC 987, June 1986.

     Kille87a.
          S.E. Kille, "Addendum to RFC 987," UK Academic Community
          Report (MG.23) / RFC 1026, August 1987.

     Kille89a.
          S.E. Kille, "A String Encoding of Presentation Address," UCL
          Research Note 89/14, March 1989.

     Kille89b.
          S.E. Kille, "Mapping between full RFC 822 and RFC 822 with
          restricted encoding," RFC 1137, October 1989.

     Kille90a.
          S.E. Kille, "Mapping Between X.400(1988) / ISO 10021 and RFC
          822," RFC 1148, March 1990.

     Larmouth83a.
          J. Larmouth, "JNT Name Registration Technical Guide,"
          Salford University Computer Centre, April 1983.

     Postel84a.
          J. Postel and J. Reynolds, "Domain Requirements," RFC 920,
          October 1984.

     Postel82a.
          J.B. Postel, "SIMPLE MAIL TRANSFER PROTOCOL," RFC 821,
          August 1982.

     Rose85a.
          M.T. Rose and E.A. Stefferud, "Proposed Standard for Message
          Encapsulation," RFC 934, January 1985.




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     Systems85a.
          CEN/CENELEC/Information Technology/Working Group on Private
          Message Handling Systems, "FUNCTIONAL STANDARD A/3222,"
          CEN/CLC/IT/WG/PMHS N 17, October 1985.











































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