Network Working Group K. Moore
Request for Comments: 3464 University of Tennessee
Obsoletes: 1894 G. Vaudreuil
Category: Standards Track Lucent Technologies
January 2003
An Extensible Message Format for Delivery Status Notifications
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This memo defines a Multipurpose Internet Mail Extensions (MIME)
content-type that may be used by a message transfer agent (MTA) or
electronic mail gateway to report the result of an attempt to deliver
a message to one or more recipients. This content-type is intended
as a machine-processable replacement for the various types of
delivery status notifications currently used in Internet electronic
mail.
Because many messages are sent between the Internet and other
messaging systems (such as X.400 or the so-called "Local Area Network
(LAN)-based" systems), the Delivery Status Notification (DSN)
protocol is designed to be useful in a multi-protocol messaging
environment. To this end, the protocol described in this memo
provides for the carriage of "foreign" addresses and error codes, in
addition to those normally used in Internet mail. Additional
attributes may also be defined to support "tunneling" of foreign
notifications through Internet mail.
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Table of Contents
1. Introduction ....................................................3
1.1 Purposes .....................................................3
1.2 Requirements .................................................4
1.3 Terminology ..................................................5
2. Format of a Delivery Status Notification ........................7
2.1 The message/delivery-status content-type .....................9
2.1.1 General conventions for DSN fields ........................9
2.1.2 "*-type" sub-fields .......................................9
2.1.3 Lexical tokens imported from RFC 822 .....................10
2.2 Per-Message DSN Fields ......................................11
2.2.1 The Original-Envelope-Id field ...........................11
2.2.2 The Reporting-MTA DSN field ..............................12
2.2.3 The DSN-Gateway field ....................................13
2.2.4 The Received-From-MTA DSN field ..........................14
2.2.5 The Arrival-Date DSN field ...............................14
2.3 Per-Recipient DSN fields ....................................14
2.3.1 Original-Recipient field .................................15
2.3.2 Final-Recipient field ....................................15
2.3.3 Action field .............................................16
2.3.4 Status field .............................................18
2.3.5 Remote-MTA field .........................................19
2.3.6 Diagnostic-Code field ....................................19
2.3.7 Last-Attempt-Date field ..................................20
2.3.8 final-log-id field .......................................20
2.3.9 Will-Retry-Until field ...................................20
2.4 Extension fields ............................................21
3. Conformance and Usage Requirements .............................22
4. Security Considerations ........................................23
4.1 Forgery .....................................................23
4.2 Confidentiality .............................................23
4.3 Non-Repudiation .............................................25
5. References .....................................................25
6. Acknowledgments ................................................26
Appendix A - Collected Grammar ....................................27
Appendix B - Guidelines for Gatewaying DSNS .......................29
Gatewaying from other mail systems to DSNs ......................29
Gatewaying from DSNs to other mail systems ......................30
Appendix C - Guidelines for Use of DSNS By Mailing List Exploders .30
Appendix D - IANA Registration Forms for DSN Types ................31
IANA registration form for address-type .........................32
IANA registration form for diagnostic-type ......................32
IANA registration form for MTA-name-type ........................32
Appendix E - Examples .............................................33
Simple DSN ......................................................34
Multi-Recipient DSN .............................................35
DSN from gateway to foreign system ..............................36
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Delayed DSN .....................................................37
Appendix F - Changes from RFC 1894 ................................38
Authors' Addresses ................................................39
Full Copyright Statement ..........................................40
1. Introduction
This memo defines a Multipurpose Internet Mail Extensions (MIME)
[MIME1] content-type for Delivery Status Notifications (DSNs). A DSN
can be used to notify the sender of a message of any of several
conditions: failed delivery, delayed delivery, successful delivery,
or the gatewaying of a message into an environment that may not
support DSNs. The "message/delivery-status" content-type defined
herein is intended for use within the framework of the
"multipart/report" content type defined in [REPORT].
This memo defines only the format of the notifications. An extension
to the Simple Message Transfer Protocol (SMTP) [SMTP] to fully
support such notifications is the subject of a separate memo [DRPT].
Document Conventions
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 BCP 14, RFC 2119
[RFC2119].
1.1 Purposes
The DSNs defined in this memo are expected to serve several purposes:
(a) Inform human beings of the status of message delivery processing,
as well as the reasons for any delivery problems or outright
failures, in a manner that is largely independent of human
language and media;
(b) Allow mail user agents to keep track of the delivery status of
messages sent, by associating returned DSNs with earlier message
transmissions;
(c) Allow mailing list exploders to automatically maintain their
subscriber lists when delivery attempts repeatedly fail;
(d) Convey delivery and non-delivery notifications resulting from
attempts to deliver messages to "foreign" mail systems via a
gateway;
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(e) Allow "foreign" notifications to be tunneled through a MIME-
capable message system and back into the original messaging
system that issued the original notification, or even to a third
messaging system;
(f) Allow language-independent and medium-independent, yet reasonably
precise, indications of the reason for the failure of a message
to be delivered; and
(g) Provide sufficient information to remote MTA maintainers (via
"trouble tickets") so that they can understand the nature of
reported errors. This feature is used in the case that failure
to deliver a message is due to the malfunction of a remote MTA
and the sender wants to report the problem to the remote MTA
administrator.
1.2 Requirements
These purposes place the following constraints on the notification
protocol:
(a) It must be readable by humans as well as being machine-parsable.
(b) It must provide enough information to allow message senders (or
the user agents) to unambiguously associate a DSN with the
message that was sent and the original recipient address for
which the DSN is issued (if such information is available), even
if the message was forwarded to another recipient address.
(c) It must be able to preserve the reason for the success or failure
of a delivery attempt in a remote messaging system, using the
"language" (mailbox addresses and status codes) of that remote
system.
(d) It must also be able to describe the reason for the success or
failure of a delivery attempt, independent of any particular
human language or of the "language" of any particular mail
system.
(e) It must preserve enough information to allow the maintainer of a
remote MTA to understand (and if possible, reproduce) the
conditions that caused a delivery failure at that MTA.
(f) For any notifications issued by foreign mail systems, which are
translated by a mail gateway to the DSN format, the DSN must
preserve the "type" of the foreign addresses and error codes, so
that these may be correctly interpreted by gateways.
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A DSN contains a set of per-message fields that identify the message
and the transaction during which the message was submitted, along
with other fields that apply to all delivery attempts described by
the DSN. The DSN also includes a set of per-recipient fields to
convey the result of the attempt to deliver the message to each of
one or more recipients.
1.3 Terminology
A message may be transmitted through several message transfer agents
(MTAs) on its way to a recipient. For a variety of reasons,
recipient addresses may be rewritten during this process, so each MTA
may potentially see a different recipient address. Depending on the
purpose for which a DSN is used, different formats of a particular
recipient address will be needed.
Several DSN fields are defined in terms of the view from a particular
MTA in the transmission. The MTAs are assigned the following names:
(a) Original MTA
The Original MTA is the one to which the message is submitted for
delivery by the sender of the message.
(b) Reporting MTA
For any DSN, the Reporting MTA is the one which is reporting the
results of delivery attempts described in the DSN.
If the delivery attempts described occurred in a "foreign" (non-
Internet) mail system, and the DSN was produced by translating
the foreign notice into DSN format, the Reporting MTA will still
identify the "foreign" MTA where the delivery attempts occurred.
(c) Received-From MTA
The Received-From MTA is the MTA from which the Reporting MTA
received the message, and accepted responsibility for delivery of
the message.
(d) Remote MTA
If an MTA determines that it must relay a message to one or more
recipients, but the message cannot be transferred to its "next
hop" MTA, or if the "next hop" MTA refuses to accept
responsibility for delivery of the message to one or more of its
intended recipients, the relaying MTA may need to issue a DSN on
behalf of the recipients for whom the message cannot be
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delivered. In this case the relaying MTA is the Reporting MTA,
and the "next hop" MTA is known as the Remote MTA.
Figure 1 illustrates the relationship between the various MTAs.
+-----+ +--------+ +---------+ +---------+ +------+
| | | | |Received-| | | | |
| | => |Original| => ... => | From | => |Reporting| ===> |Remote|
| user| | MTA | | MTA | | MTA | ".
A particular DSN describes the delivery status for exactly one
message. However, an MTA MAY report on the delivery status for
several recipients of the same message in a single DSN. Due to the
nature of the mail transport system (where responsibility for
delivery of a message to its recipients may be split among several
MTAs, and delivery to any particular recipient may be delayed),
multiple DSNs may still be issued in response to a single message
submission.
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2.1 The message/delivery-status content-type
The message/delivery-status content-type is defined as follows:
MIME type name: message
MIME subtype name: delivery-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 message/delivery-status report type for use in the
multipart/report is "delivery-status".
The body of a message/delivery-status consists of one or more
"fields" formatted according to the ABNF of RFC 822 header "fields"
(see [RFC822]). 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. Using the ABNF of RFC 822, the syntax of
the message/delivery-status content is as follows:
delivery-status-content = per-message-fields 1*
( CRLF per-recipient-fields )
The per-message fields are described in section 2.2. The
per-recipient fields are described in section 2.3.
2.1.1 General conventions for DSN fields
Since these fields are defined according to the rules of RFC 822, the
same conventions for continuation lines and comments apply.
Notification fields may be continued onto multiple lines by beginning
each additional line with a SPACE or HTAB. Text that appears in
parentheses is considered a comment and not part of the contents of
that notification field. Field names are case-insensitive, so the
names of notification fields may be spelled in any combination of
upper and lower case letters. Comments in DSN fields may use the
"encoded-word" construct defined in [MIME3].
2.1.2 "*-type" sub-fields
Several DSN fields consist of a "-type" sub-field, followed by a
semicolon, followed by "*text". For these fields, the keyword used
in the address-type, diagnostic-type, or MTA-name-type sub-field
indicates the expected format of the address, status-code, or
MTA-name which follows.
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The "-type" sub-fields are defined as follows:
(a) An "address-type" specifies the format of a mailbox address. For
example, Internet mail addresses use the "rfc822" address-type.
address-type = atom
(b) A "diagnostic-type" specifies the format of a status code. For
example, when a DSN field contains a reply code reported via the
Simple Mail Transfer Protocol [SMTP], the "smtp" diagnostic-type
is used.
diagnostic-type = atom
(c) An "MTA-name-type" specifies the format of an MTA name. For
example, for an SMTP server on an Internet host, the MTA name is
the domain name of that host, and the "dns" MTA-name-type is
used.
mta-name-type = atom
Values for address-type, diagnostic-type, and MTA-name-type are
case-insensitive. Thus address-type values of "RFC822" and "rfc822"
are equivalent.
The Internet Assigned Numbers Authority (IANA) will maintain a
registry of address-types, diagnostic-types, and MTA-name-types,
along with descriptions of the meanings and acceptable values of
each, or a reference to one or more specifications that provide such
descriptions. (The "rfc822" address-type, "smtp" diagnostic-type,
and "dns" MTA-name-type are defined in [DRPT].) Registration forms
for address-type, diagnostic-type, and MTA-name-type appear in
Appendix D.
IANA will not accept registrations for any address-type,
diagnostic-type, or MTA-name-type name that begins with "X-". These
type names are reserved for experimental use.
2.1.3 Lexical tokens imported from RFC 822
The following lexical tokens, defined in [RFC822], are used in the
ABNF grammar for DSNs: atom, CHAR, comment, CR, CRLF, DIGIT, LF,
linear-white-space, SPACE, text. The date-time lexical token is
defined in [HOSTREQ].
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2.2 Per-Message DSN Fields
Some fields of a DSN apply to all of the delivery attempts described
by that DSN. At most, these fields may appear once in any DSN.
These fields are used to correlate the DSN 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
[ dsn-gateway-field CRLF ]
[ received-from-mta-field CRLF ]
[ arrival-date-field CRLF ]
*( extension-field CRLF )
2.2.1 The Original-Envelope-Id field
The optional Original-Envelope-Id field contains an "envelope
identifier" that uniquely identifies the transaction during which the
message was submitted, and was either (a) specified by the sender and
supplied to the sender's MTA, or (b) generated by the sender's MTA
and made available to the sender when the message was submitted. Its
purpose is to allow the sender (or her user agent) to associate the
returned DSN with the specific transaction in which the message was
sent.
If such an envelope identifier was present in the envelope that
accompanied the message when it arrived at the Reporting MTA, it
SHOULD be supplied in the Original-Envelope-Id field of any DSNs
issued as a result of an attempt to deliver the message. Except when
a DSN is issued by the sender's MTA, an MTA MUST NOT supply this
field unless there is an envelope-identifier field in the envelope
that accompanied this message on its arrival at the Reporting MTA.
The Original-Envelope-Id field is defined as follows:
original-envelope-id-field =
"Original-Envelope-Id" ":" envelope-id
envelope-id = *text
There may be at most one Original-Envelope-Id field per DSN.
The envelope-id is CASE-SENSITIVE. The DSN MUST preserve the
original case and spelling of the envelope-id.
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NOTE: The Original-Envelope-Id is NOT the same as the
Message-Id from the message header. The Message-Id identifies
the content of the message, while the Original-Envelope-Id
identifies the transaction in which the message is sent.
2.2.2 The Reporting-MTA DSN field
reporting-mta-field =
"Reporting-MTA" ":" mta-name-type ";" mta-name
mta-name = *text
The Reporting-MTA field is defined as follows:
A DSN describes the results of attempts to deliver, relay, or gateway
a message to one or more recipients. In all cases, the Reporting-MTA
is the MTA that attempted to perform the delivery, relay, or gateway
operation described in the DSN. This field is required.
Note that if an SMTP client attempts to relay a message to an SMTP
server and receives an error reply to a RCPT command, the client is
responsible for generating the DSN, and the client's domain name will
appear in the Reporting-MTA field. (The server's domain name will
appear in the Remote-MTA field.)
Note that the Reporting-MTA is not necessarily the MTA which actually
issued the DSN. For example, if an attempt to deliver a message
outside of the Internet resulted in a non-delivery notification which
was gatewayed back into Internet mail, the Reporting-MTA field of the
resulting DSN would be that of the MTA that originally reported the
delivery failure, not that of the gateway which converted the foreign
notification into a DSN. See Figure 2.
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sender's environment recipient's environment
............................ ..........................................
: :
(1) : : (2)
+-----+ +--------+ +--------+ +---------+ +---------+ +------+
| | | | | | |Received-| | | | |
| |=>|Original|=>| |->| From |->|Reporting|-->|Remote|
| user| | MTA | | | | MTA | | MTA |") (so that no DSNs would be sent from a
downstream MTA to the original sender),
(e) for messages forwarded to a confidential address, disabling
delivery notifications for the forwarded message (e.g., if the
"next-hop" MTA uses ESMTP and supports the DSN extension, by
using the NOTIFY=NEVER parameter to the RCPT command), or
(f) when forwarding mail to a confidential address, having the
forwarding MTA rewrite the envelope return address for the
forwarded message and attempt delivery of that message as if the
forwarding MTA were the originator. On its receipt of final
delivery status, the forwarding MTA would issue a DSN to the
original sender.
In general, any optional DSN field may be omitted if the Reporting
MTA site determines that inclusion of the field would impose too
great a compromise of site confidentiality. The need for such
confidentiality must be balanced against the utility of the omitted
information in trouble reports and DSNs gatewayed to foreign
environments.
Implementers are cautioned that many existing MTAs will send non-
delivery notifications to a return address in the message header
(rather than to the one in the envelope), in violation of SMTP and
other protocols. If a message is forwarded through such an MTA, no
reasonable action on the part of the forwarding MTA will prevent the
downstream MTA from compromising the forwarding address. Likewise,
if the recipient's MTA automatically responds to messages based on a
request in the message header (such as the nonstandard, but widely
used, Return-Receipt-To extension header), it will also compromise
the forwarding address.
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4.3 Non-Repudiation
Within the framework of today's internet mail, the DSNs defined in
this memo provide valuable information to the mail user; however,
even a "failed" DSN can not be relied upon as a guarantee that a
message was not received by the recipient. Even if DSNs are not
actively forged, conditions exist under which a message can be
delivered despite the fact that a failure DSN was issued.
For example, a race condition in the SMTP protocol allows for the
duplication of messages if the connection is dropped following a
completed DATA command, but before a response is seen by the SMTP
client.
This will cause the SMTP client to retransmit the message, even
though the SMTP server has already accepted it [SMTPDUP]. If one of
those delivery attempts succeeds and the other one fails, a "failed"
DSN could be issued even though the message actually reached the
recipient.
5. Normative References
[DRPT] Moore, K., "SMTP Service Extension for Delivery Status
Notifications", RFC 3461, January 2003.
[DSN] Moore, K. and G. Vaudreuil, "An Extensible Message Format
for Delivery Status Notifications", RFC 1894, January 1996.
[HOSTREQ] Braden, R. (ed.), "Requirements for Internet Hosts -
Application and Support", STD 3, RFC 1123, October 1989.
[MIME1] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[MIME3] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text",
RFC 2047, November 1996.
[REPORT] Vaudreuil, G., "The Multipart/Report Content Type for the
Reporting of Mail System Administrative Messages", RFC
3462, January 2003.
[RFC822] Crocker, D., "Standard for the format of ARPA Internet Text
Messages", STD 11, RFC 822, August 1982.
[SMTP] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC
821, August 1982.
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[SMTPDUP] Partridge, C., "Duplicate Messages and SMTP", RFC 1047,
February 1988.
[STATUS] Vaudreuil, G., "Enhanced Mail System Status Codes", RFC
3463, January 2003.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
6. Acknowledgments
The authors wish to thank the following people for their reviews of
early drafts of RFC 1894, of which this document is a revision, and
their suggestions for improvement: Eric Allman, Harald Alvestrand,
Allan Cargille, Jim Conklin, Peter Cowen, Dave Crocker, Roger Fajman,
Ned Freed, Marko Kaittola, Steve Kille, John Klensin, John Gardiner
Myers, Mark Nahabedian, Julian Onions, Jacob Palme, Jean Charles Roy,
and Gregory Sheehan.
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Appendix A - collected grammar
NOTE: The following lexical tokens are defined in RFC 822: atom,
CHAR, comment, CR, CRLF, DIGIT, LF, linear-white-space, SPACE, text.
The date-time lexical token is defined in [HOSTREQ].
action-field = "Action" ":" action-value
action-value = "failed" / "delayed" / "delivered"
/ "relayed" / "expanded"
address-type = atom
arrival-date-field = "Arrival-Date" ":" date-time
delivery-status-content = per-message-fields
1*( CRLF per-recipient-fields )
diagnostic-code-field = "Diagnostic-Code" ":"
diagnostic-type ";" *text
diagnostic-type = atom
dsn-gateway-field = "DSN-Gateway" ":" mta-name-type ";" mta-name
envelope-id = *text
extension-field = extension-field-name ":" *text
extension-field-name = atom
final-recipient-field =
"Final-Recipient" ":" address-type ";" generic-address
final-log-id-field = "Final-Log-ID" ":" *text
generic-address = *text
last-attempt-date-field = "Last-Attempt-Date" ":" date-time
mta-name = *text
mta-name-type = atom
original-envelope-id-field =
"Original-Envelope-Id" ":" envelope-id
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original-recipient-field =
"Original-Recipient" ":" address-type ";" generic-address
per-message-fields =
[ original-envelope-id-field CRLF ]
reporting-mta-field CRLF
[ dsn-gateway-field CRLF ]
[ received-from-mta-field CRLF ]
[ arrival-date-field CRLF ]
*( extension-field CRLF )
per-recipient-fields =
[ original-recipient-field CRLF ]
final-recipient-field CRLF
action-field CRLF
status-field CRLF
[ remote-mta-field CRLF ]
[ diagnostic-code-field CRLF ]
[ last-attempt-date-field CRLF ]
[ final-log-id-field CRLF ]
[ will-retry-until-field CRLF ]
*( extension-field CRLF )
received-from-mta-field =
"Received-From-MTA" ":" mta-name-type ";" mta-name
remote-mta-field =
"Remote-MTA" ":" mta-name-type ";" mta-name
reporting-mta-field =
"Reporting-MTA" ":" mta-name-type ";" mta-name
status-code = DIGIT "." 1*3DIGIT "." 1*3DIGIT
; White-space characters and comments are NOT allowed within a
; a status-code, though a comment enclosed in parentheses
; MAY follow the last numeric sub-field of the status-code.
; Each numeric sub-field within the status-code MUST be
; expressed without leading zero digits.
status-field = "Status" ":" status-code
will-retry-until-field = "Will-Retry-Until" ":" date-time
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Appendix B - Guidelines for gatewaying DSNs
NOTE: This section provides non-binding recommendations for the
construction of mail gateways that wish to provide semi-transparent
delivery reports between the Internet and another electronic mail
system. Specific DSN gateway requirements for a particular pair of
mail systems may be defined by other documents.
Gatewaying from other mail systems to DSNs
A mail gateway may issue a DSN to convey the contents of a "foreign"
delivery or non-delivery notification over Internet mail. When there
are appropriate mappings from the foreign notification elements to
DSN fields, the information may be transmitted in those DSN fields.
Additional information (such as might be useful in a trouble ticket
or needed to tunnel the foreign notification through the Internet)
may be defined in extension DSN fields. (Such fields should be given
names that identify the foreign mail protocol, e.g., X400-* for X.400
NDN or DN protocol elements)
The gateway must attempt to supply reasonable values for the
Reporting-MTA, Final-Recipient, Action, and Status fields. These
will normally be obtained by translating the values from the remote
delivery or non-delivery notification into their Internet-style
equivalents. However, some loss of information is to be expected.
For example, the set of status-codes defined for DSNs may not be
adequate to fully convey the delivery diagnostic code from the
foreign system. The gateway should assign the most precise code
which describes the failure condition, falling back on "generic"
codes such as 2.0.0 (success), 4.0.0 (temporary failure), and 5.0.0
(permanent failure) when necessary. The actual foreign diagnostic
code should be retained in the Diagnostic-Code field (with an
appropriate diagnostic-type value) for use in trouble tickets or
tunneling.
The sender-specified recipient address, and the original envelope-id,
if present in the foreign transport envelope, should be preserved in
the Original-Recipient and Original-Envelope-ID fields.
The gateway should also attempt to preserve the "final" recipient
addresses and MTA names from the foreign system. Whenever possible,
foreign protocol elements should be encoded as meaningful printable
ASCII strings.
For DSNs produced from foreign delivery or nondelivery notifications,
the name of the gateway MUST appear in the DSN-Gateway field of the
DSN.
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Gatewaying from DSNs to other mail systems
It may be possible to gateway DSNs from the Internet into a foreign
mail system. The primary purpose of such gatewaying is to convey
delivery status information in a form that is usable by the
destination system. A secondary purpose is to allow "tunneling" of
DSNs through foreign mail systems, in case the DSN may be gatewayed
back into the Internet.
In general, the recipient of the DSN (i.e., the sender of the
original message) will want to know, for each recipient: the closest
available approximation to the original recipient address, the
delivery status (success, failure, or temporary failure), and for
failed deliveries, a diagnostic code that describes the reason for
the failure.
If possible, the gateway should attempt to preserve the Original-
Recipient address and Original-Envelope-ID (if present), in the
resulting foreign delivery status report.
When reporting delivery failures, if the diagnostic-type sub-field of
the Diagnostic-Code field indicates that the original diagnostic code
is understood by the destination environment, the information from
the Diagnostic-Code field should be used. Failing that, the
information in the Status field should be mapped into the closest
available diagnostic code used in the destination environment.
If it is possible to tunnel a DSN through the destination
environment, the gateway specification may define a means of
preserving the DSN information in the delivery status reports used by
that environment.
Appendix C - Guidelines for use of DSNs by mailing list exploders
This section pertains only to the use of DSNs by "mailing lists" as
defined in [4], section 7.2.7.
DSNs are designed to be used by mailing list exploders to allow them
to detect and automatically delete recipients for whom mail delivery
fails repeatedly.
When forwarding a message to list subscribers, the mailing list
exploder should always set the envelope return address (e.g., SMTP
MAIL FROM address) to point to a special address which is set up to
receive non-delivery reports. A "smart" mailing list exploder can
therefore intercept such non-delivery reports, and if they are in the
DSN format, automatically examine them to determine for which
recipients a message delivery failed or was delayed.
Moore & Vaudreuil Standards Track [Page 30]
RFC 3464 Delivery Status Notifications January 2003
The Original-Recipient field should be used if available, since it
should exactly match the subscriber address known to the list. If
the Original-Recipient field is not available, the recipient field
may resemble the list subscriber address. Often, however, the list
subscriber will have forwarded his mail to a different address, or
the address may be subject to some re-writing, so heuristics may be
required to successfully match an address from the recipient field.
Care is needed in this case to minimize the possibility of false
matches.
The reason for delivery failure can be obtained from the Status and
Action fields, and from the Diagnostic-Code field (if the status-type
is recognized). Reports for recipients with action values other than
"failed" can generally be ignored; in particular, subscribers should
not be removed from a list due to "delayed" reports.
In general, almost any failure status code (even a "permanent" one)
can result from a temporary condition. It is therefore recommended
that a list exploder not delete a subscriber based on any single
failure DSN (regardless of the status code), but only on the
persistence of delivery failure over a period of time.
However, some kinds of failures are less likely than others to have
been caused by temporary conditions, and some kinds of failures are
more likely to be noticed and corrected quickly than others. Once
more precise status codes are defined, it may be useful to
differentiate between the status codes when deciding whether to
delete a subscriber. For example, on a list with a high message
volume, it might be desirable to temporarily suspend delivery to a
recipient address which causes repeated "temporary" failures, rather
than simply deleting the recipient. The duration of the suspension
might depend on the type of error. On the other hand, a "user
unknown" error that persisted for several days could be considered a
reliable indication that address were no longer valid.
Appendix D - IANA registration forms for DSN types
The forms below are for use when registering a new address-type,
diagnostic-type, or MTA-name-type with the Internet Assigned Numbers
Authority (IANA). Each piece of information requested by a
registration form may be satisfied either by providing the
information on the form itself, or by including a reference to a
published, publicly available specification which includes the
necessary information. IANA MAY reject DSN type registrations
because of incomplete registration forms, imprecise specifications,
or inappropriate type names.
Moore & Vaudreuil Standards Track [Page 31]
RFC 3464 Delivery Status Notifications January 2003
To register a DSN type, complete the applicable form below and send
it via Internet electronic mail to .
IANA registration form for address-type
A registration for a DSN address-type MUST include the following
information:
(a) The proposed address-type name.
(b) The syntax for mailbox addresses of this type, specified using
BNF, regular expressions, ASN.1, or other non-ambiguous language.
(c) If addresses of this type are not composed entirely of graphic
characters from the US-ASCII repertoire, a specification for how
they are to be encoded as graphic US-ASCII characters in a DSN
Original-Recipient or Final-Recipient DSN field.
(d) [optional] A specification for how addresses of this type are to
be translated to and from Internet electronic mail addresses.
IANA registration form for diagnostic-type
A registration for a DSN address-type MUST include the following
information:
(a) The proposed diagnostic-type name.
(b) A description of the syntax to be used for expressing diagnostic
codes of this type as graphic characters from the US-ASCII
repertoire.
(c) A list of valid diagnostic codes of this type and the meaning of
each code.
(d) [optional] A specification for mapping from diagnostic codes of
this type to DSN status codes (as defined in [5]).
IANA registration form for MTA-name-type
A registration for a DSN MTA-name-type must include the following
information:
(a) The proposed MTA-name-type name.
(b) A description of the syntax of MTA names of this type, using BNF,
regular expressions, ASN.1, or other non-ambiguous language.
Moore & Vaudreuil Standards Track [Page 32]
RFC 3464 Delivery Status Notifications January 2003
(c) If MTA names of this type do not consist entirely of graphic
characters from the US-ASCII repertoire, a specification for how
an MTA name of this type should be expressed as a sequence of
graphic US-ASCII characters.
Appendix E - Examples
These examples are provided as illustration only, and are not
considered part of the DSN protocol specification. If an example
conflicts with the protocol definition above, the example is wrong.
Likewise, the use of *-type sub-field names or extension fields in
these examples is not to be construed as a definition for those type
names or extension fields.
These examples were manually translated from bounced messages using
whatever information was available.
Moore & Vaudreuil Standards Track [Page 33]
RFC 3464 Delivery Status Notifications January 2003
Simple DSN
This is a simple DSN issued after repeated attempts to deliver a
message failed. In this case, the DSN is issued by the same MTA from
which the message was originated.
Date: Thu, 7 Jul 1994 17:16:05 -0400 From: Mail Delivery Subsystem
Message-Id:
<199407072116.RAA14128@CS.UTK.EDU> Subject: Returned mail: Cannot
send message for 5 days To: MIME-
Version: 1.0 Content-Type: multipart/report; report-type=delivery-
status;
boundary="RAA14128.773615765/CS.UTK.EDU"
--RAA14128.773615765/CS.UTK.EDU
The original message was received at Sat, 2 Jul 1994 17:10:28 -0400
from root@localhost
----- The following addresses had delivery problems -----
(unrecoverable error)
----- Transcript of session follows -----
... Deferred: Connection timed out
with larry.slip.umd.edu.
Message could not be delivered for 5 days
Message will be deleted from queue
--RAA14128.773615765/CS.UTK.EDU
content-type: message/delivery-status
Reporting-MTA: dns; cs.utk.edu
Original-Recipient: rfc822;louisl@larry.slip.umd.edu
Final-Recipient: rfc822;louisl@larry.slip.umd.edu
Action: failed
Status: 4.0.0
Diagnostic-Code: smtp; 426 connection timed out
Last-Attempt-Date: Thu, 7 Jul 1994 17:15:49 -0400
--RAA14128.773615765/CS.UTK.EDU
content-type: message/rfc822
[original message goes here]
--RAA14128.773615765/CS.UTK.EDU--
Moore & Vaudreuil Standards Track [Page 34]
RFC 3464 Delivery Status Notifications January 2003
Multi-Recipient DSN
This is another DSN issued by the sender's MTA, which contains
details of multiple delivery attempts. Some of these were detected
locally, and others by a remote MTA.
Date: Fri, 8 Jul 1994 09:21:47 -0400
From: Mail Delivery Subsystem
Subject: Returned mail: User unknown
To:
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
boundary="JAA13167.773673707/CS.UTK.EDU"
--JAA13167.773673707/CS.UTK.EDU
content-type: text/plain; charset=us-ascii
----- The following addresses had delivery problems -----
(unrecoverable error)
(unrecoverable error)
--JAA13167.773673707/CS.UTK.EDU
content-type: message/delivery-status
Reporting-MTA: dns; cs.utk.edu
Original-Recipient: rfc822;arathib@vnet.ibm.com
Final-Recipient: rfc822;arathib@vnet.ibm.com
Action: failed
Status: 5.0.0 (permanent failure)
Diagnostic-Code: smtp; 550 'arathib@vnet.IBM.COM' is not a
registered gateway user
Remote-MTA: dns; vnet.ibm.com
Original-Recipient: rfc822;johnh@hpnjld.njd.hp.com
Final-Recipient: rfc822;johnh@hpnjld.njd.hp.com
Action: delayed
Status: 4.0.0 (hpnjld.njd.jp.com: host name lookup failure)
Original-Recipient: rfc822;wsnell@sdcc13.ucsd.edu
Final-Recipient: rfc822;wsnell@sdcc13.ucsd.edu
Action: failed
Status: 5.0.0
Diagnostic-Code: smtp; 550 user unknown
Remote-MTA: dns; sdcc13.ucsd.edu
--JAA13167.773673707/CS.UTK.EDU
content-type: message/rfc822
Moore & Vaudreuil Standards Track [Page 35]
RFC 3464 Delivery Status Notifications January 2003
[original message goes here]
--JAA13167.773673707/CS.UTK.EDU--
DSN from gateway to foreign system
A delivery report generated by Message Router (MAILBUS) and gatewayed
by PMDF_MR to a DSN. In this case the gateway did not have
sufficient information to supply an original-recipient address.
Disclose-recipients: prohibited
Date: Fri, 08 Jul 1994 09:21:25 -0400 (EDT)
From: Message Router Submission Agent
Subject: Status of: Re: Battery current sense
To: owner-ups-mib@CS.UTK.EDU
Message-id: <01HEGJ0WNBY28Y95LN@mr.timeplex.com>
MIME-version: 1.0
content-type: multipart/report;
report-type=delivery-status;
boundary="84229080704991.122306.SYS30"
--84229080704991.122306.SYS30
content-type: text/plain
Invalid address - nair_s
%DIR-E-NODIRMTCH, No matching Directory Entry
Entry found
--84229080704991.122306.SYS30
content-type: message/delivery-status
Reporting-MTA: mailbus; SYS30
Final-Recipient: unknown; nair_s
Status: 5.0.0 (unknown permanent failure)
Action: failed
--84229080704991.122306.SYS30--
Moore & Vaudreuil Standards Track [Page 36]
RFC 3464 Delivery Status Notifications January 2003
Delayed DSN
A delay report from a multiprotocol MTA. Note that there is no
returned content, so no third body part appears in the DSN.
MIME-Version: 1.0
From:
Message-Id: <199407092338.TAA23293@CS.UTK.EDU>
Received: from nsfnet-relay.ac.uk by sun2.nsfnet-relay.ac.uk
id ;
Sun, 10 Jul 1994 00:36:51 +0100
To: owner-info-mime@cs.utk.edu
Date: Sun, 10 Jul 1994 00:36:51 +0100
Subject: WARNING: message delayed at "nsfnet-relay.ac.uk"
content-type: multipart/report; report-type=delivery-status;
boundary=foobar
--foobar
content-type: text/plain
The following message:
UA-ID: Reliable PC (...
Q-ID: sun2.nsf:77/msg.11820-0
has not been delivered to the intended recipient:
thomas@de-montfort.ac.uk
despite repeated delivery attempts over the past 24 hours.
The usual cause of this problem is that the remote system is
temporarily unavailable.
Delivery will continue to be attempted up to a total elapsed time of
168 hours, i.e., 7 days.
You will be informed if delivery proves to be impossible within this
time.
Please quote the Q-ID in any queries regarding this mail.
--foobar
content-type: message/delivery-status
Reporting-MTA: dns; sun2.nsfnet-relay.ac.uk
Final-Recipient: rfc822;thomas@de-montfort.ac.uk
Moore & Vaudreuil Standards Track [Page 37]
RFC 3464 Delivery Status Notifications January 2003
Status: 4.0.0 (unknown temporary failure)
Action: delayed
--foobar--
Appendix F - Changes from RFC 1894
Changed Authors contact information
Updated required standards boilerplate
Edited the text to make it spell-checker and grammar checker
compliant
Updated references to point to later, more mature documents, changed
reference enumeration scheme.
Fixed paragraph numbering on page 20
Fixed Delayed DSN example
Added Table of Contents
Moved Appendices to the end of the document
Changed the MTA-name-Type for gateways into Internet mail, the
MTA-name-type from "SMTP" to "dns".
Moore & Vaudreuil Standards Track [Page 38]
RFC 3464 Delivery Status Notifications January 2003
Authors' Addresses
Keith Moore
University of Tennessee
1122 Volunteer Blvd, Suite 203
Knoxville TN 37996-3450
USA
Phone: +1-865-974-3126
Fax: +1-865-974-8296
EMail: moore@cs.utk.edu
Gregory M. Vaudreuil
Lucent Technologies
7291 Williamson Rd
Dallas, Tx. 75214
USA
Phone: +1 214 823 9325
EMail: GregV@ieee.org
Moore & Vaudreuil Standards Track [Page 39]
RFC 3464 Delivery Status Notifications January 2003
Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Moore & Vaudreuil Standards Track [Page 40]
RFC, FYI, BCP