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Versions: 02 03 04 05 rfc1891                                           
Network Working Group                                        Keith Moore
Internet-Draft                                   University of Tennessee
Expires: May 20, 1995                                  November 20, 1994


                         SMTP Service Extension
                   for Delivery Status Notifications

                   draft-ietf-notary-smtp-drpt-02.txt


1. Status of this Memo

   This document is an Internet-Draft.  Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, and
its working groups.  Note that other groups may also distribute working
documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time.  It is not appropriate to use Internet-Drafts as reference
material or to cite them other than as ``work in progress.''

   To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet- Drafts Shadow
Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
ftp.isi.edu (US West Coast).


2. Abstract

   This memo defines an extension to the SMTP service, which allow an
SMTP client to specify (a) that delivery status notifications (DSNs)
should be generated under certain conditions, (b) whether such
notifications should return the contents of the message, and (c)
additional information, to be returned with a DSN, that allows the
sender to identify both the recipient and the transaction in which the
message was sent.


3. Introduction

   The SMTP protocol [1] requires that an SMTP server provide
notification of delivery failure, if it determines that a message cannot
be delivered to one or more recipients.  Traditionally, such
notification consists of an ordinary Internet mail message (format
defined by [2]), sent to the envelope sender address (the argument of
the SMTP MAIL command), containing an explanation of the error and at
least the headers the failed message.

   Experiences with large mail distribution lists [3] indicates that
such messages are often insufficient to diagnose problems, or even to
determine at which host or for which recipients a problem occurred.  In
addition, the lack of a standardized format for delivery notifications



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in Internet mail makes it difficult to exchange such notifications with
other message handling systems.

   Such experience has demonstrated a need for a delivery status
notification service for Internet electronic mail, which:

(a) is reliable, in the sense that any DSN request will either be
    honored at the time of final delivery, or result in a response that
    indicates that the request cannot be honored,

(b) should result in exactly one response for any particular sender-
    specified recipient,

(c) is stable, in that a DSN should never be issued in response to a
    DSN.

(d) preserves sufficient information to allow the sender to identify
    both the mail transaction and the recipient address which caused the
    notification, even when mail is forwarded or gatewayed to foreign
    environments, and

(e) interfaces acceptably with non-SMTP and non-822-based mail systems,
    both so that notifications returned from foreign mail systems may be
    useful to Internet users, and so that the notification requests from
    foreign environments may be honored.  Among the requirements implied
    by this goal are the ability to request non-return-of-content, and
    the ability to specify whether positive or negative delivery
    notifications, or both, or neither, should be issued.

   In an attempt to provide such a service, this memo uses the mechanism
defined in [4] to define an extension to the SMTP protocol.  Using this
mechanism, an SMTP client may request that an SMTP server issue or not
issue a delivery status notification (DSN) under certain conditions.
The format of a DSN is defined in [5].


4. Framework for the Delivery Status Notification Extension

   The following service extension is therefore defined:

(1) The name of the SMTP service extension is "Delivery Status
    Notification";

(2) the EHLO keyword value associated with this extension is "DSN", the
    meaning of which is defined in section 5 of this memo;

(3) no parameters are allowed with this EHLO keyword value;

(4) three optional parameters are added to the RCPT command, and two
    optional parameters are added to the MAIL command:




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    An optional parameter for the RCPT command, using the esmtp-keyword
    "NOTIFY", (to specify the conditions under which a delivery status
    notification should be generated), is defined in section 6.1,

    An optional parameter for the RCPT command, using the esmtp-keyword
    "RET", (to request that DSNs either return or not return the
    contents of a message), is defined in section 6.2,

    An optional parameter for the RCPT command, using the esmtp-keyword
    "ORCPT", (used to convey the "original" (sender-specified) recipient
    address), is defined in section 6.3, and

    An optional parameter for the MAIL command, using the esmtp-keyword
    "OMTS", (used to specify the type of message transfer system in
    which the message originated), is defined in section 6.4, and

    An optional parameter for the MAIL command, using the esmtp-keyword
    "ENVID", (used to propagate a sender-specified unique identifier for
    this envelope, to be returned in a DSN), is defined in section 6.5;

(5) no additional SMTP verbs are defined by this extension.

   The remainder of this memo specifies how support for the extension
affects the behavior of a message transfer agent.


5.  The Delivery Status Notification service extension

   An SMTP client wishing to request a DSN for a message may issue the
EHLO command to start an SMTP session, to determine if the server
supports any of several service extensions.  If the server responds with
code 250 to the EHLO command, and the response includes the EHLO keyword
DSN, then the Delivery Status Notification extension (as described in
this memo) is supported.

   Ordinarily, when an SMTP server returns a positive (2xx) reply code
in response to a RCPT command, it agrees to accept responsibility for
either delivering the message to the named recipient, or sending a
notification to the sender of the message indicating that delivery has
failed.  However, an extended SMTP ("ESMTP") server which implements
this service extension will accept an optional NOTIFY parameter with the
RCPT command. If present, the NOTIFY parameter alters the default
conditions for generation of delivery status notifications from the
default (issue notifications only on failure) specified in [1].  The
ESMTP client may also request (via the RET parameter) whether the entire
contents of the original message should be returned (as opposed to just
the headers of that message), along with the DSN.

   In general, an ESMTP server which implements this service extension
will propagate delivery status notification requests when relaying mail
to other SMTP-based MTAs which also support this extension, and make a



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"best effort" to ensure that such requests are honored when messages are
passed into other environments.

   In order that any delivery status notifications thus generated will
be meaningful to the sender, any ESMTP server which supports this
extension will attempt to propagate the following information to any
other MTAs that are used to relay the message, for use in generating
DSNs:

(a) for each recipient, a copy of the original recipient address, as
    used by the sender of the message.

    This address need not be the same as the mailbox specified in the
    RCPT command.  For example, the addresses will be different if the
    message was forwarded from the sender-specified address to another
    address, or the message originated in a foreign environment that
    does not use Internet electronic mail addresses.

(b) for the entire SMTP transaction, an envelope identification string,
    which may be used by the sender to associate any delivery status
    notifications with the transaction used to send the original
    message.


6.  Additional parameters for RCPT and MAIL commands

   The extended RCPT and MAIL commands are issued by a client when it
wishes to request a DSN from the server, under certain conditions, for a
particular recipient.  The extended RCPT and MAIL commands are identical
to the RCPT and MAIL commands defined in [1], except that one or more of
the following parameters appear after the sender or recipient address,
respectively.  The general syntax for extended SMTP commands is defined
in [4].


6.1.  The NOTIFY parameter of the ESMTP RCPT command

   A RCPT command issued by a client may contain the optional esmtp-
keyword "NOTIFY", to specify the conditions under which the SMTP server
should generate DSNs for that recipient.  If the NOTIFY esmtp-keyword is
used, it MUST have an associated esmtp-value, formatted according to the
following rules, using the ABNF of RFC 822:

     notify-esmtp-value = "NEVER" / 1#notify-list-element

     notify-list-element = "SUCCESS" / "FAILURE" / "DELAY"

Notes:
1. Multiple notify-list-elements, separated by commas, may appear in a
   NOTIFY parameter; however, the NEVER keyword may only appear by
   itself.



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2. Any of the keywords NEVER, SUCCESS, FAILURE, or DELAY may be spelled
   in any combination of upper and lower case letters.
3. Although RFC 822 ABNF syntax is used, RFC 822 style comments may not
   appear in NOTIFY parameter values.

The meaning of the NOTIFY parameter values is generally as follows:
+ If the esmtp-value consists of the keyword "NEVER", a DSN should not
  be issued under any conditions.
+ If on the other hand, the esmtp-value contains one or more of the
  keywords "SUCCESS" or "FAILURE", a DSN should be issued on successful
  delivery or delivery failure, respectively.
+ If the esmtp-value contains the keyword "DELAY", a "delayed" DSN MAY
  be issued if a message cannot be delivered or relayed for an extended
  period of time, as determined by the MTA at which the message is
  delayed.  The absence of the DELAY keyword in a NOTIFY parameter
  implies that a "delayed" DSN SHOULD NOT be issued under any
  conditions.

If the NOTIFY parameter is not included in a RCPT command, the SMTP
server should issue notifications for that recipient only if the message
cannot be delivered, as specified in [1].


6.2 The RET parameter of the ESMTP RCPT command

   The RET esmtp-keyword on the extended RCPT command specifies whether
or not the message should be included in any DSN issued for this
recipient.  If the RET esmtp-keyword is used, it MUST have an associated
esmtp-value, which should contain one of the following keywords:

FULL requests that the message be returned in any delivery status
     notification issued for this recipient.
HDRS requests that only the headers of the message not be returned.

   The RET parameter is optional; it need not be specified to request a
DSN.  If the RET parameter was not specified for a particular recipient,
the MTA issuing the notification may choose to return either the entire
content, or only the headers of the original message.


6.3 The ORCPT parameter to the ESMTP RCPT command

   The ORCPT esmtp-keyword of the RCPT command is used to specify an
"original" recipient address that corresponds to the actual recipient to
which the message is to be delivered.   If the ORCPT esmtp-keyword is
used, it MUST have an associated esmtp-value, which consists of the
original recipient address, encoded according to the rules below.

IMPORTANT:  Because a message may have originated in a foreign
environment that does not use Internet-style electronic mail addresses,
the esmtp-value associated with the ORCPT keyword is NOT constrained to



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conform to syntax rules for Internet addresses.

   Ideally, the esmtp-value associated with this parameter should
contain (in encoded form) the same sequence of characters that the
sender used to specify the recipient.  However, for a message gatewayed
from an environment (such as X.400) in which a recipient address is not
a simple string of printable characters, the ORCPT parameter should
contain a printable representation of the recipient address that is
likely to be recognized by the sender.

   Any valid esmtp-value (as defined in [4]) may be associated with the
ORCPT keyword.  However, the syntax for an esmtp-value does not allow
the use of certain characters.  Since such characters might appear in
the original recipient address, the following scheme is used to encode
the original recipient address into a valid esmtp-value:

1. Any graphic ASCII character (range 32-126 inclusive), except for "=",
   SP, and "%", may be encoded as itself.

2. Any octet value may be encoded using the percent character ("%")
   followed by two hex digits.

   The ORCPT parameter is optional.  It should not be supplied by the
SMTP client if the original recipient address (or a reasonable
printable-text representation thereof) is not available to the client.


6.4  The OMTS parameter to the ESMTP MAIL command

   The OMTS esmtp-keywoard of the SMTP MAIL command is used to specify
the "original MTS type", which identifies the type of mail system from
which the message originated, and will appear in the Original-MTS-Type
field in any DSNs generated for this message.

   The OMTS esmtp-keyword must have an associated esmtp-value.  The
esmtp-value associated with this parameter must be a legal MTS-type, as
defined in [5].

   Note:  The definition of the MTS-type indicated by the OMTS esmtp-
keyword may specify the syntax of recipient addresses to be used in
Delivery Status Notifications.  Whenever a foreign address does not
consist entirely of printable ASCII characters, the definition of the
sender's MTS-type (as supplied in the OMTS parameter) governs how such
foreign addresses are expressed via the ORCPT parameter as well as in
DSNs.

   The OMTS parameter is optional.  It should not be supplied to an SMTP
server if the original MTS-type is not known by the client.






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6.5  The ENVID parameter to the ESMTP MAIL command

   The ENVID esmtp-keyword of the SMTP MAIL command is used to specify
an "envelope identifier" to be transmitted along with the message and
included in any DSNs issued for any of the recipients named in this SMTP
transaction.  The purpose of the envelope identifier is to allow the
sender of a message to identify the transaction for which the DSN was
issued.

   The ENVID esmtp-keyword MUST have an associated esmtp-value.  No
meaning is assigned by the mail system to the presence or absence of
this parameter or to any esmtp-value associated with this parameter; the
information is used only by the sender or his user agent.

   Use of the ENVID esmtp-keyword is optional.  It need not be specified
to request a DSN.


6.6. Restrictions on the use of Delivery Status Notification parameters

   No more than one each of the OMTS and ENVID parameters may appear in
a single MAIL command.  If more than one of either of these parameters
appears in a MAIL command, the ESMTP server should respond with "501
syntax error in parameters or arguments".

   No more than one each of the NOTIFY, RET, and ORCPT parameters may
appear in any RCPT command.  If multiple occurrences of any of these
parameters appear in a RCPT command, the ESMTP server should respond
with "501 syntax error in parameters or arguments".


7. MTA conformance requirements

   Typically, a message transfer agent (MTA) which supports SMTP will
assume, at different times, both the role of a SMTP client and an SMTP
server, and may also provide local delivery, gatewaying to foreign
environments, forwarding, and mailing list expansion.  An MTA which, (in
its role as an SMTP server) issues the DSN keyword in response to the
EHLO command, MUST obey the rules below for a "conforming MTA" below.
The terms "conforming SMTP client" and "conforming SMTP server" refer to
a "conforming MTA" when acting in the role of an SMTP server or client,
respectively.


7.1 ESMTP protocol interactions

   The following rules apply to ESMTP transactions in which any of the
OMTS, ENVID, NOTIFY, RET, or ORCPT keywords are used:

1. If an SMTP client issues a MAIL command containing a valid ENVID
   parameter and associated esmtp-value and/or a valid OMTS parameter



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   and associated esmtp-value, a conforming ESMTP server MUST return the
   same reply-code as it would to the same MAIL command without the
   ENVID and/or OMTS parameters.  A conforming SMTP server MAY NOT
   refuse a MAIL command based on the presence or absence of ENVID or
   OMTS parameters, or on their associated esmtp-values.

   However, if the associated esmtp-keyword is not valid (i.e. contains
   illegal characters), or if there is more than one ENVID or OMTS
   parameter in a particular MAIL command, the server should issue the
   response "501 syntax error in parameter".

2. If an SMTP client issues a RCPT command containing any valid NOTIFY,
   RET, and/or ORCPT parameters, a conforming SMTP server MUST return
   the same response as it would to the same RCPT command without those
   NOTIFY, RET, and ORCPT parameters.  A conforming SMTP server MAY NOT
   refuse a RCPT command based on the presence or absence of any of
   these parameters.

   However, if any of the associated esmtp-keywords are not valid, or if
   there is more than one of any of these parameters in a particular
   RCPT command, the server should issue the response "501 syntax error
   in parameter".


7.2. Handling of messages received via SMTP

   This section describes how a conforming MTA should handle any
messages received via SMTP.


7.2.1. Relay of messages to other conforming SMTP servers

   The following rules govern the behavior of a conforming SMTP client,
when relaying a message which was received via the SMTP protocol, to an
SMTP server that supports the Delivery Status Notification service
extension:

1. Any ENVID parameter included in the MAIL command when a message was
   received, must also appear on the MAIL command with which the message
   is relayed, with the same associated esmtp-value.  If no ENVID
   parameter was included in the MAIL command when the message was
   received, no ENVID parameter shall be supplied when the message is
   relayed.

2. Any OMTS parameter included in the MAIL command when a message was
   received, must also appear on the MAIL command with which the message
   is relayed, with the same associated esmtp-value.  If not OMTS
   parameter was included in the MAIL command when the message was
   received, no OMTS parameter shall be supplied when the message is
   relayed.




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3. If the NOTIFY parameter was supplied for a recipient when the message
   was received, the RCPT command issued when the message is relayed
   must also contain the NOTIFY parameter along with its associated
   esmtp-value.  If any RET or ORCPT parameters were present in the RCPT
   command for this recipient when the message was received, they must
   also appear in the RCPT command issued when relaying the message.
   When relaying a message to a particular recipient, no NOTIFY, RET, or
   ORCPT parameters may be supplied which were not present in the RCPT
   command for that recipient when the message was received.


7.2.2.  Relay of messages to non-conforming SMTP servers

   The following rules govern the behavior of a conforming SMTP client,
when relaying a message which was received via the SMTP protocol, to an
SMTP server that does not support the Delivery Status Notification
service extension:

1. No ENVID, OMTS, NOTIFY, RET, or ORCPT parameters may be issued when
   relaying the message.

2. If the NOTIFY parameter was supplied for a recipient, with an esmtp-
   value containing the keyword SUCCESS, and the SMTP server returns a
   success (2XX) reply-code in response to the RCPT command, the client
   must issue a "relayed" DSN for that recipient.

3. If the NOTIFY parameter was supplied for a recipient with an esmtp-
   value containing the keyword FAILURE, and the SMTP server returns a
   permanent failure (5XX) reply-code in response to the RCPT command,
   the client must issue a "failed" DSN for that recipient.

4. If the NOTIFY parameter was supplied for a recipient with an esmtp-
   value of NEVER, no DSN is issued, regardless of the reply-code
   returned by the SMTP server.

5. If a NOTIFY parameter was not supplied for a recipient, and the SMTP
   server returns a success (2xx) reply-code in response to a RCPT
   command, the client must not issue any DSN for that recipient.

6. If a NOTIFY parameter was not supplied for a recipient, and the SMTP
   server returns a permanent failure (5XX) reply-code in response to a
   RCPT command, the client must issue a "failed" DSN for that
   recipient.


7.2.3.  Local delivery of messages

   The following rules govern the behavior of a conforming MTA upon
successful delivery of a message that was received via the SMTP
protocol, to a local recipient's mailbox:




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1. If the NOTIFY parameter was supplied for that recipient, with an
   esmtp-value containing the SUCCESS keyword, the MTA must issue a
   "delivered" DSN for that recipient.

2. If the NOTIFY parameter was supplied for that recipient with an
   esmtp-value of NEVER, no DSN is issued.

3. If the NOTIFY parameter was not supplied for that recipient, no DSN
   is issued.


7.2.4.  Gatewaying a message into a foreign environment

   The following rules govern the behavior of a conforming MTA, when
gatewaying a message that was received via the SMTP protocol, into a
foreign (non-SMTP) environment:

1. If the the foreign environment is capable of issuing appropriate
   notifications under the conditions requested by the NOTIFY parameter,
   and the conforming MTA can ensure that any notification thus issued
   will be translated into a DSN and delivered to the original sender,
   then the MTA should gateway the message into the foreign environment,
   requesting notification under the desired conditions, without itself
   issuing a DSN.

2. If a NOTIFY parameter was supplied with either or both of the SUCCESS
   or FAILURE keywords, but the requested conditions specified by the
   associated esmtp-value cannot be met by the foreign mail environment,
   the MTA should issue a "relayed" DSN for that recipient.

3. If a NOTIFY parameter was supplied with an esmtp-keyword of NEVER, no
   DSN should be issued.

4. If the NOTIFY parameter was not supplied for a particular recipient,
   no DSN should be issued by the gateway, but the gateway should
   attempt to ensure that appropriate notification will be provided by
   the foreign mail environment if eventual delivery failure occurs.

5. When gatewaying a message into a foreign environment, the return-of-
   content conditions specified by any RET parameter are nonbinding;
   however, the MTA should attempt to honor the request using whatever
   mechanisms exist in the foreign environment.


7.2.5.  Delays in delivery

   A conforming MTA which receives a message via the SMTP protocol which
is unable to deliver a message to one or more recipients for an extended
length of time (to be determined by the MTA), may issue a "delayed" DSN
for those recipients, under the following conditions:




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1. If the NOTIFY parameter was supplied for a recipient and its value
   included the DELAY keyword, a "delayed" DSN may be issued.

2. If the NOTIFY parameter was not supplied for a recipient, a "delayed"
   DSN may be issued.

3. If the NOTIFY parameter was supplied which did not contain the DELAY
   keyword, a "delayed" DSN may not be issued.

NOTE: Although delay notifications are common in present-day email, a
conforming MTA is never required to issue "delayed" DSNs.  The DELAY
keyword of the NOTIFY parameter is provided to allow the SMTP client to
specifically request (by omitting the DELAY parameter) that "delayed"
DSNs NOT be issued.


7.2.6.  Failure of a conforming MTA to deliver a message

   The following rules govern the behavior of a conforming MTA which
received a message via the SMTP protocol, and is unable to deliver a
message to a recipient specified in the SMTP transaction:

1. If a NOTIFY parameter was supplied for the recipient with an esmtp-
   keyword containing the value FAILURE, a "failed" DSN should be issued
   by the MTA.

2. If a NOTIFY parameter was supplied for the recipient which did not
   contain the value FAILURE, no DSN should be issued for that
   recipient.

3. If no NOTIFY parameter was supplied for the recipient, a "failure"
   DSN should be issued.


7.2.7.  Recipient-specified mail forwarding

   If a message intended for a particular recipient address is to be
"forwarded" to exactly one recipient address:

1. Any envelope-id and original-mts-type included with the message as
   received, should be propagated in each ESMTP session used to forward
   the message to a conforming MTA.

2. Any NOTIFY, ORCPT, or RET parameters associated with a particular
   recipient should be propagated, for each of the recipients to which
   the message is forwarded.

   However, if the message is to be forwarded to multiple recipient
addresses on behalf of a single recipient, a "delivered" DSN should be
issued, and the request for a DSN should NOT be propagated to the
recipient's forwarding addresses.



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(NOTE IN DRAFT: this is intended to ensure exactly one notification per
request.  I'm concerned that DSNs will be difficult to use by mailing
list exploders if it's possible to get more than one notification per
request, say because a message was forwarded to two recipients, and
delivery succeeds for one and fails for the other.  On the other hand,
it's still possible to get both a "relayed" or "delivered" DSN and
afterwards a "failed" DSN for the same recipient, and a foreign mail
system might not issue DSNs for forwarded messages and deliveries to
lists.)


7.2.8.  Delivery of a message to a mailing list

   If a particular recipient address refers to a mailing list, a message
is considered to be successfully delivered to that recipient if the MTA
determines that the message is eligible to be distributed to the members
of the list.  If a NOTIFY parameter was supplied with an esmtp-value
which contains the value SUCCESS, a "delivered" DSN should be issued.
Any envelope-id, original-mts-type, notify-request, return-of-content-
request, or original-recipient-address should NOT be propagated when
delivering a message to the recipients of that list.

   If the message is not eligible to be distributed to the list
membership (perhaps because the sender is not authorized), and either a
NOTIFY parameter was supplied which contained the FAILURE keyword, or no
NOTIFY parameter was supplied, a "failed" DSN should be issued.


7.3. Handling of messages from other sources

   For messages which originated from "local" users (whatever that
means), the specifications under which DSNs should be generated can be
communicated to the MTA via any protocol agreed on between the sender's
mail composer (user agent) and the MTA.  The local MTA can then either
relay the message, or issue appropriate delivery status notifications.
However, if such requests are transmitted within the message itself (for
example in the headers), the requests MUST be removed from the message
before it is transmitted via SMTP.

   For messages gatewayed from non-SMTP sources and further relayed by
SMTP, the gateway should, using the SMTP extensions described here,
attempt to provide the delivery reporting conditions expected by the
source mail environment.  If appropriate, any DSNs returned to the
source environment should be translated into the format expected in that
environment.


8.  Format of delivery notifications

   The format of delivery status notifications is defined in [5], which
uses the framework defined in [6].  Delivery status notifications are to



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be returned to the sender of the original message according as outlined
below.


8.1. SMTP Envelope to be used with delivery status notifications

   The sender address (in the SMTP MAIL command) must be an empty
string.  The recipient address (in the RCPT command) is copied from the
MAIL command of the message for which a delivery notification is being
issued.  The envelope of a delivery notification may not use the DSN
option.


8.2. Contents of the DSN

   A DSN is transmitted as a MIME message with a top-level content-type
of multipart/report (as defined in [6]).

   The multipart/report content-type may be used for any of several
kinds of reports generated by the mail system.  When multipart/report is
used to convey a DSN, the report-type parameter of the multipart/report
content-type must be "delivery-status".

   As described in [6], the first component of a multipart/report
content-type is a human readable explanation of the report.  For a DSN,
the second component of the multipart/report is of content-type
message/delivery-status (defined in [5]).  The third component of the
multipart/report consists of the returned message (or only the headers).


8.3. Message/delivery-status fields

   The multipart/delivery-status content-type defines a number of
fields, with general specifications for their contents.  When generating
a DSN for a message which was received via the SMTP protocol, a
conforming MTA will generate the per-message fields of the
multipart/delivery-status body part as follows:

(a) if an ENVID parameter was present on the MAIL command, an Original-
    Envelope-ID field must be supplied, and the value associated with
    the ENVID parameter must appear in that field.

(b) if an OMTS parameter was present on the MAIL command, an Original-
    MTS-Type field must be supplied, and the value associated with the
    OMTS parameter must appear in that field.

(c) The Final-MTA field must be supplied, and it must contain the domain
    name of the SMTP server which is actually issuing this notification.

(d) The Final-MTS-Type field must be supplied.  For DSNs generated for
    messages received by SMTP, the Final-MTS-Type will normally be



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    "Internet".

(e) Other per-message fields as defined in [5] MAY be supplied.

(f) If the ORCPT parameter was provided for this recipient, the
    Original-Recipient field should appear, with its value taken from
    the ORCPT parameter.

(g) If the OMTS parameter was provided for this recipient, the Original-
    MTS-Type field must appear, with its value taken from the OMTS
    paramter.

(h) For DSNs resulting from attempts to relay a message to a recipient
    via SMTP, the Remote-* fields must be supplied.  In this case,
    Remote-MTS-Type will normally be "Internet".

(i) Other per-recipient fields defined in [5] may also appear, as
    appropriate.


9. Acknowledgments

   (fill in this space)


10. References

[1] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
    USC/Information Sciences Institute, August 1982.

[2] Crocker, D., "Standard for the Format of ARPA Internet Text
    Messages", STD 11, RFC 822, UDEL, August 1982.

[3] Westine, A., Postel, J. "Problems with the Maintenance of Large
    Mailing Lists.", RFC 1211, USC/Information Sciences Institute, March
    1991.

[4] Klensin, J., Freed, N., Rose, M., Stefferud, E., Crocker., D.  "SMTP
    Service Extensions", RFC 1651, MCI, Innosoft, Dover Beach
    Consulting, Inc., Network Management Associates, Inc., Silicon
    Graphics, Inc., July 1994.

[5] Moore, K., Vaudreuil, G.  "An Extensible Message Format for Delivery
    Status Notifications".  Internet-Draft "draft-ietf-notary-mime-
    delivery-03.txt", 20 November 1994.

[6] Vaudreuil, G.  "Multipart/Report".  Internet-Draft "draft-ietf-
    notary-mime-report-00.txt", 1 August 1994.






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11. Author's address

Keith Moore
University of Tennessee
107 Ayres Hall
Knoxville, TN 37996-1301
USA

email: moore@cs.utk.edu













































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APPENDIX: Summary of changes since draft-ietf-notary-smtp-drpt-01.txt

1. Added OMTS esmtp-keyword to convey Original-MTS-Type.
2. Changed syntax of NOTIFY parameters to be either a comma-separated
   list from the set SUCCESS, FAILURE, DELAY, or the single keyword
   NEVER.
3. Changed syntax of RET parameter to specify either return of
   content or return of headers only.
4. Updated to reflect the current DSN and multipart/report drafts.
5. Updated references.












































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