Internet DRAFT - draft-ietf-msgtrk-trkstat


Internet Draft                                               E. Allman
draft-ietf-msgtrk-trkstat-05.txt                        Sendmail, Inc.
Valid for six months                                    March 19, 2003
Updates: RFC 1893

     An Extensible Message Format for Message Tracking Responses


Status of This Memo

     This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026.  Internet-Drafts are
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Internet Draft          Message/Tracking-Status         March 19, 2003

to the mailing list.  An archive of the mailing
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     Distribution of this memo is unlimited.

1.  Abstract

        Message Tracking is expected to be used to determine the
   status of undelivered e-mail upon request.  Tracking is used in
   conjunction with Delivery Status Notifications [RFC-DSN-SMTP] and
   Message Disposition Notifications [RFC-MDN]; generally, a message
   tracking request will be issued only when a DSN or MDN has not been
   received within a reasonable timeout period.

        This memo defines a MIME [RFC-MIME] content-type for message
   tracking status in the same spirit as RFC 1894, ``An Extensible
   Message Format for Delivery Status Notifications'' [RFC-DSN-STAT].
   It is to be issued upon a request as described in ``Message
   Tracking Query Protocol'' [DRAFT-MTRK-MTQP].  This memo defines
   only the format of the status information.  An extension to SMTP
   [RFC-ESMTP] to label messages for further tracking and request
   tracking status is defined in a separate memo [DRAFT-MTRK-SMTPEXT].

2.  Other Documents and Conformance

        The model used for Message Tracking is described in [DRAFT-

        Message tracking is intended for use as a "last resort"
   mechanism.  Normally, Delivery Status Notifications (DSNs) [RFC-
   DSN-SMTP] and Message Disposition Notifications (MDNs) [RFC-MDN]
   would provide the primary delivery status.  Only if no response is
   received from either of these mechanisms would Message Tracking be

        This document is based on [RFC-DSN-STAT].  Sections 1.3
   (Terminology), 2.1.1 (General conventions for DSN fields), 2.1.2
   ("*-type" subfields), and 2.1.3 (Lexical tokens imported from RFC
   822) of [RFC-DSN-STAT] are included into this document by
   reference.  Other sections are further incorporated as described

        Syntax notation in this document conforms to [RFC-ABNF].

        The following lexical tokens, defined in [RFC-MSGFMT], are
   used in the ABNF grammar for MTSNs: atom, CHAR, comment, CR, CRLF,
   DIGIT, LF, linear-white-space, SPACE, text.  The date-time lexical
   token is defined in [RFC-HOSTREQ].

        The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
   in this document are to be interpreted as described in RFC 2119

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3.  Format of a Message Tracking Status Notification

        A Message Tracking Status Notification (MTSN) is intended to
   be returned as the body of a Message Tracking request [DRAFT-MTRK-
   MTQP].  The actual body MUST be a multipart/related [RFC-RELATED]
   with type parameter of "message/tracking-status"; each subpart MUST
   be of type "message/tracking-status" as described herein.  The
   multipart/related body can include multiple message/tracking-status
   parts if an MTQP server chains requests to the next server; see
   [DRAFT-MTRK-MODEL] and [DRAFT-MTRK-MTQP] for more information about

   3.1.  The message/tracking-status content-type

           The message/tracking-status content-type is defined as

          MIME type name:           message
          MIME subtype name:        tracking-status
          Optional parameters:      none
          Encoding considerations:  "7bit" encoding is sufficient and
                                    MUST be used to maintain readability
                                    when viewed by non-MIME mail readers.
          Security considerations:  discussed in section 4 of this memo.

           The body of a message/tracking-status is modeled after
      [RFC-DSN-STAT].  That body consists of one or more "fields"
      formatted to according to the ABNF of RFC 2822 header "fields"
      (see [RFC-MSGFMT]).  The per-message fields appear first,
      followed by a blank line.  Following the per-message fields are
      one or more groups of per-recipient fields.  Each group of per-
      recipient fields is preceded by a blank line.  Note that there
      will be a blank line between the final per-recipient field and
      the MIME boundary, since one CRLF is necessary to terminate the
      field, and a second is necessary to introduce the MIME boundary.
      Formally, the syntax of the message/tracking-status content is
      as follows:

          tracking-status-content =
                    per-message-fields 1*( CRLF per-recipient-fields )

      The per-message fields are described in section 3.2.  The per-
      recipient fields are described in section 3.3.

      3.1.1.  General conventions for MTSN fields

              Section 2.1.1 (General conventions for DSN fields) of
         [RFC-DSN-STAT] is included herein by reference.  Notably, the
         definition of xtext is identical to that of that document.

      3.1.2.  *-type subfields

              Section 2.1.2 (*-type subfields) of [RFC-DSN-STAT] is
         included herein by reference.  Notably, the definitions of
         address-type, diagnostic-type, and MTA-name type are

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         identical to that of RFC 1894.

   3.2.  Per-Message MTSN Fields

           Some fields of an MTSN apply to all of the addresses in a
      single envelope.  These fields may appear at most once in any
      MTSN.  These fields are used to correlate the MTSN with the
      original message transaction and to provide additional
      information which may be useful to gateways.

          per-message-fields =
                    original-envelope-id-field CRLF
                    reporting-mta-field CRLF
                    arrival-date-field CRLF
                    *( extension-field CRLF )

      3.2.1.  The Original-Envelope-Id field

              The Original-Envelope-Id field is defined as in section
         2.2.1 of [RFC-DSN-STAT].  This field is REQUIRED.

      3.2.2.  The Reporting-MTA field

              The Reporting-MTA field is defined as in section 2.2.2
         of [RFC-DSN-STAT].  This field is REQUIRED.

      3.2.3.  The Arrival-Date field

              The Arrival-Date field is defined as in section 2.2.5 of
         [RFC-DSN-STAT].  This field is REQUIRED.

   3.3.  Per-Recipient MTSN fields

           An MTSN contains information about attempts to deliver a
      message to one or more recipients.  The delivery information for
      any particular recipient is contained in a group of contiguous
      per-recipient fields.  Each group of per-recipient fields is
      preceded by a blank line.

           The syntax for the group of per-recipient fields is as

          per-recipient-fields =
                    original-recipient-field CRLF
                    final-recipient-field CRLF
                    action-field CRLF
                    status-field CRLF
                    [ remote-mta-field CRLF ]
                    [ last-attempt-date-field CRLF ]
                    [ will-retry-until-field CRLF ]
                    *( extension-field CRLF )

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      3.3.1.  Original-Recipient field

              The Original-Recipient field is defined as in section
         2.3.1 of [RFC-DSN-STAT].  This field is REQUIRED.

      3.3.2.  Final-Recipient field

              The required Final-Recipient field is defined as in
         section 2.3.2 of [RFC-DSN-STAT].  This field is REQUIRED.

      3.3.3.  Action field

              The required Action field indicates the action performed
         by the Reporting-MTA as a result of its attempt to deliver
         the message to this recipient address.  This field MUST be
         present for each recipient named in the MTSN.  The syntax is
         as defined in section 2.3.3 of RFC 1894.  This field is

              Valid actions are:

         failed       The message could not be delivered.  If DSNs
                      have been enabled, a "failed" DSN should already
                      have been returned.

         delayed      The message is currently waiting in the MTA
                      queue for future delivery.  Essentially, this
                      action means "the message is located, and it is

         delivered    The message has been successfully delivered to
                      the final recipient.  This includes "delivery"
                      to a mailing list exploder.  It does not
                      indicate that the message has been read.  No
                      further information is available; in particular,
                      the tracking agent SHOULD NOT attempt further
                      "downstream" tracking requests.

         expanded     The message has been successfully delivered to
                      the recipient address as specified by the
                      sender, and forwarded by the Reporting-MTA
                      beyond that destination to multiple additional
                      recipient addresses.  However, these additional
                      addresses are not trackable, and the tracking
                      agent SHOULD NOT attempt further "downstream"
                      tracking requests.

         relayed      The message has been delivered into an
                      environment that does not support message
                      tracking.  No further information is available;
                      in particular, the tracking agent SHOULD NOT
                      attempt further "downstream" tracking requests.

         transferred  The message has been transferred to another
                      MTRK-compliant MTA.  The tracking agent SHOULD
                      attempt further "downstream" tracking requests

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                      unless that information is already given in a
                      chaining response.

         opaque       The message may or may not have been seen by
                      this system.  No further information is
                      available or forthcoming.

              There may be some confusion between when to use
         "expanded" versus "delivered".  Whenever possible, "expanded"
         should be used when the MTA knows that the message will be
         sent to multiple addresses.  However, in some cases the
         delivery occurs to a program which, unknown to the MTA,
         causes mailing list expansion; in the extreme case, the
         delivery may be to a real mailbox that has the side effect of
         list expansion.  If the MTA cannot ensure that this delivery
         will cause list expansion, it should set the action to

      3.3.4.  Status field

              The Status field is defined as in RFC 1894 section
         2.3.4.  A new code is added to RFC 1893 [RFC-EMSSC],
         "Enhanced Mail System Status Codes",

             X.1.9   Message relayed to non-compliant mailer"

                 The mailbox address specified was valid, but the
                 message has been relayed to a system that does not
                 speak this protocol; no further information can be
         A 2.1.9 Status field MUST be used exclusively with a
         "relayed" Action field.  This field is REQUIRED.

      3.3.5.  Remote-MTA field

              The Remote-MTA field is defined as in section Reference
         2.3.5 of [RFC-DSN-STAT].  This field MUST NOT be included if
         no delivery attempts have been made or if the Action field
         has value "opaque".  If delivery to some agent other than an
         MTA (for example, a Local Delivery Agent) then this field MAY
         be included, giving the name of the host on which that agent
         was contacted.

      3.3.6.  Last-Attempt-Date field

              The Last-Attempt-Date field is defined as in section
         Reference 2.3.7 of [RFC-DSN-STAT].  This field is REQUIRED if
         any delivery attempt has been made and the Action field does
         not have value "opaque", in which case it will specify when
         it last attempted to deliver this message to another MTA or
         other Delivery Agent.  This field MUST NOT be included if no
         delivery attempts have been made.

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      3.3.7.  Will-Retry-Until field

              The Will-Retry-Until field is defined as in section
         Reference 2.3.8 of [RFC-DSN-STAT].  If the message is not in
         the local queue or the Action field has the value ``opaque''
         the Will-Retry-Until field MUST NOT be included; otherwise,
         this field SHOULD be included.

   3.4.  Extension fields

           Future extension fields may be defined as defined in
      section 2.4 of [RFC-DSN-STAT].

   3.5.  Interaction Between MTAs and LDAs

           A message that has been delivered to a Local Delivery Agent
      (LDA) that understands message tracking (in particular, an LDA
      speaking LMTP [RFC-LMTP] that supports the MTRK extension)
      SHOULD pass the tracking request to the LDA.  In this case, the
      Action field for the MTA->LDA exchange will look the same as a
      transfer to a compliant MTA; that is, a "transferred" tracking
      status will be issued.

4.  Security Considerations

   4.1.  Forgery

           Malicious servers may attempt to subvert message tracking
      and return false information.  This could result in misdirection
      or misinterpretation of results.

   4.2.  Confidentiality

           Another dimension of security is confidentiality.  There
      may be cases in which a message recipient is autoforwarding
      messages but does not wish to divulge the address to which the
      messages are autoforwarded.  The desire for such confidentiality
      will probably be heightened as "wireless mailboxes", such as
      pagers, become more widely used as autoforward addresses.

           MTA authors are encouraged to provide a mechanism which
      enables the end user to preserve the confidentiality of a
      forwarding address.  Depending on the degree of confidentiality
      required, and the nature of the environment to which a message
      were being forwarded, this might be accomplished by one or more

      (a)  respond with a "relayed" tracking status when a message is
           forwarded to a confidential forwarding address, and
           disabling further message tracking requests.

      (b)  declaring the message to be delivered, issuing a
           "delivered" tracking status, re-sending the message to the
           confidential forwarding address, and disabling further
           message tracking requests.

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           The tracking algorithms MUST NOT allow tracking through
      list expansions.  When a message is delivered to a list, a
      tracking request MUST respond with an "expanded" tracking status
      and MUST NOT display the contents of the list.

5.  IANA Considerations

        IANA is to register the SMTP extension defined in section 3.

6.  Acknowledgements

        Several individuals have commented on and enhanced this draft,
   including Tony Hansen, Philip Hazel, Alexey Melnikov, Lyndon
   Nerenberg, Chris Newman, Gregory Neil Shapiro, and Dan Wing.

7.  Normative References

        T. Hansen, ``Message Tracking Model and Requirements.''
        draft-ietf-msgtrk-model-03.txt.  November 2000.

        T. Hansen, ``Message Tracking Query Protocol.''  draft-ietf-
        msgtrk-mtqp-01.txt.  November 2000.

        E. Allman, ``SMTP Service Extension for Message Tracking.''
        draft-ietf-msgtrk-smtpext-05.txt.  March 2003.

        Crocker, D., Editor, and P. Overell, ``Augmented BNF for
        Syntax Specifications: ABNF'', RFC 2234, November 1997.

        G. Vaudreuil, ``Enhanced Mail System Status Codes.''  RFC
        1893.  January 1996.

        R. Braden (ed.), ``Requirements for Internet Hosts --
        Application and Support.''  STD 3, RFC 1123.  October 1989.

        S. Bradner, ``Key words for use in RFCs to Indicate
        Requirement Levels.''  RFC 2119.  March 1997.

        N. Freed and N. Borenstein, ``Multipurpose Internet Mail
        Extensions (MIME) Part One: Format of Internet Message
        Bodies.''  RFC 2045.  November 1996.

        P. Resnick, editor, ``Internet Message Format.''  RFC 2822.
        April 2001.

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        E. Levinson, ``The MIME Multipart/Related Content-type.''  RFC
        2387.  August 1998.

8.  Informational References

        K. Moore, ``SMTP Service Extension for Delivery Status
        Notifications.''  RFC 1891.  January 1996.

        K. Moore and G. Vaudreuil, ``An Extensible Message Format for
        Delivery Status Notifications.''  RFC 1894.  January 1996.

        Rose, M., Stefferud, E., Crocker, D., Klensin, J. and N.
        Freed, ``SMTP Service Extensions.''  STD 10, RFC 1869.
        November 1995.

        J. Myers, ``Local Mail Transfer Protocol.''  RFC 2033.
        October 1996.

        R. Fajman, ``An Extensible Message Format for Message
        Disposition Notifications.''  RFC 2298.  March 1998.

9.  Author's Address

       Eric Allman
       Sendmail, Inc.
       6425 Christie Ave, 4th Floor
       Emeryville, CA  94608

       E-Mail: eric@Sendmail.COM
       Phone: +1 510 594 5501
       Fax: +1 510 594 5429

Allman                                                        [Page 9]