Internet DRAFT - draft-ietf-msgtrk-trkstat
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
<draft-ietf-msgtrk-trkstat-05.txt>
Status of This Memo
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This document is a submission by the MSGTRK Working Group of the
Internet Engineering Task Force (IETF). Comments should be submitted
Internet Draft Message/Tracking-Status March 19, 2003
to the ietf-msgtrk@imc.org mailing list. An archive of the mailing
list may be found at
http://www.imc.org/ietf-msgtrk/index.html
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-
MTRK-MODEL].
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
used.
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
herein.
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
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described in RFC 2119
[RFC-KEYWORDS].
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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
chaining.
3.1. The message/tracking-status content-type
The message/tracking-status content-type is defined as
follows:
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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Internet Draft Message/Tracking-Status March 19, 2003
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
follows:
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
REQUIRED.
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
here."
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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Internet Draft Message/Tracking-Status March 19, 2003
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
"delivered".
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
provided.
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
of:
(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
[DRAFT-MTRK-MODEL]
T. Hansen, ``Message Tracking Model and Requirements.''
draft-ietf-msgtrk-model-03.txt. November 2000.
[DRAFT-MTRK-MTQP]
T. Hansen, ``Message Tracking Query Protocol.'' draft-ietf-
msgtrk-mtqp-01.txt. November 2000.
[DRAFT-MTRK-SMTPEXT]
E. Allman, ``SMTP Service Extension for Message Tracking.''
draft-ietf-msgtrk-smtpext-05.txt. March 2003.
[RFC-ABNF]
Crocker, D., Editor, and P. Overell, ``Augmented BNF for
Syntax Specifications: ABNF'', RFC 2234, November 1997.
[RFC-EMSSC]
G. Vaudreuil, ``Enhanced Mail System Status Codes.'' RFC
1893. January 1996.
[RFC-HOSTREQ]
R. Braden (ed.), ``Requirements for Internet Hosts --
Application and Support.'' STD 3, RFC 1123. October 1989.
[RFC-KEYWORDS]
S. Bradner, ``Key words for use in RFCs to Indicate
Requirement Levels.'' RFC 2119. March 1997.
[RFC-MIME]
N. Freed and N. Borenstein, ``Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies.'' RFC 2045. November 1996.
[RFC-MSGFMT]
P. Resnick, editor, ``Internet Message Format.'' RFC 2822.
April 2001.
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[RFC-RELATED]
E. Levinson, ``The MIME Multipart/Related Content-type.'' RFC
2387. August 1998.
8. Informational References
[RFC-DSN-SMTP]
K. Moore, ``SMTP Service Extension for Delivery Status
Notifications.'' RFC 1891. January 1996.
[RFC-DSN-STAT]
K. Moore and G. Vaudreuil, ``An Extensible Message Format for
Delivery Status Notifications.'' RFC 1894. January 1996.
[RFC-ESMTP]
Rose, M., Stefferud, E., Crocker, D., Klensin, J. and N.
Freed, ``SMTP Service Extensions.'' STD 10, RFC 1869.
November 1995.
[RFC-LMTP]
J. Myers, ``Local Mail Transfer Protocol.'' RFC 2033.
October 1996.
[RFC-MDN]
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
U.S.A.
E-Mail: eric@Sendmail.COM
Phone: +1 510 594 5501
Fax: +1 510 594 5429
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