RFC1891 - SMTP Service Extension for Delivery Status Notifications

Network Working Group K. Moore

Request for Comments: 1891 University of Tennessee

Category: Standards Track January 1996

SMTP Service Extension

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.

1. Abstract

This memo defines an extension to the SMTP service, which allows 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(s) for which the DSN was

issued, and the transaction in which the original message was sent.

Any questions, comments, and reports of defects or ambiguities in

this specification may be sent to the mailing list for the NOTARY

working group of the IETF, using the address

<notifications@cs.utk.edu>. Requests to subscribe to the mailing

list should be addressed to <notifications-request@cs.utk.edu>.

Implementors of this specification are encouraged to subscribe to the

mailing list, so that they will quickly be informed of any problems

which might hinder interoperability.

NOTE: This document is a Proposed Standard. If and when this

protocol is submitted for Draft Standard status, any normative text

(phrases containing SHOULD, SHOULD NOT, MUST, MUST NOT, or MAY) in

this document will be re-evaluated in light of implementation

eXPerience, and are thus subject to change.

2. 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 of the failed message.

Experience 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 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) when both success and failure notifications are requested,

provides an unambiguous and nonconflicting indication of whether

delivery of a message to a recipient succeeded or failed,

result in the transmission of another DSN over the network,

(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 delivery notifications, negative delivery notifications,

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].

3. 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 4 of this memo;

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

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

optional parameters are added to the MAIL command:

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 5.1,

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 5.2,

and

An optional parameter for the MAIL command, using the

esmtp-keyword "RET", (to request that DSNs containing an

indication of delivery failure either return the entire contents

of a message or only the message headers), is defined in section

5.3,

An optional parameter for the MAIL command, using the

esmtp-keyword "ENVID", (used to propagate an identifier for this

message transmission envelope, which is also known to the sender

and will, if present, be returned in any DSNs issued for this

transmission), is defined in section 5.4;

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

The remainder of this memo specifies how support for the extension

effects the behavior of a message transfer agent.

4. 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 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 "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, if a message was originally addressed

to A@B.C and later forwarded to A@D.E, after such forwarding has

taken place, the RCPT command will specify a mailbox of A@D.E.

However, the original recipient address remains A@B.C.

Also, if the message originated from an environment which does not

use Internet-style user@domain addresses, and was gatewayed into

SMTP, the original recipient address will preserve the original

form of the recipient address.

(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.

5. 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].

NOTE: Although RFC822 ABNF is used to describe the syntax of these

parameters, they are not, in the language of that document,

"structured field bodies". Therefore, while parentheses MAY appear

within an emstp-value, they are not recognized as comment delimiters.

The syntax for "esmtp-value" in [4] does not allow SP, "=", control

characters, or characters outside the traditional ASCII range of 1-

127 decimal to be transmitted in an esmtp-value. Because the ENVID

and ORCPT parameters may need to convey values outside this range,

the esmtp-values for these parameters are encoded as "xtext".

"xtext" is formally defined as follows:

xtext = *( xchar / hexchar )

xchar = any ASCII CHAR between "!" (33) and "~" (126) inclusive,

except for "+" and "=".

; "hexchar"s are intended to encode octets that cannot appear

; as ASCII characters within an esmtp-value.

hexchar = ASCII "+" immediately followed by two upper case

hexadecimal digits

When encoding an octet sequence as xtext:

+ Any ASCII CHAR between "!" and "~" inclusive, except for "+" and "=",

MAY be encoded as itself. (A CHAR in this range MAY instead be

encoded as a "hexchar", at the implementor's discretion.)

+ ASCII CHARs that fall outside the range above must be encoded as

"hexchar".

5.1 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:

a. Multiple notify-list-elements, separated by commas, MAY appear in a

NOTIFY parameter; however, the NEVER keyword MUST appear by itself.

b. Any of the keywords NEVER, SUCCESS, FAILURE, or DELAY may be spelled

in any combination of upper and lower case letters.

The meaning of the NOTIFY parameter values is generally as follows:

+ A NOTIFY parameter value of "NEVER" requests that a DSN not be

returned to the sender under any conditions.

+ A NOTIFY parameter value containing the "SUCCESS" or "FAILURE"

keywords requests that a DSN be issued on successful delivery or

delivery failure, respectively.

+ A NOTIFY parameter value containing the keyword "DELAY" indicates the

sender's willingness to receive "delayed" DSNs. Delayed DSNs may be

issued if delivery of a message has been delayed for an unusual amount

of time (as determined by the MTA at which the message is delayed),

but the final delivery status (whether successful or failure) cannot

be determined. The absence of the DELAY keyword in a NOTIFY parameter

requests that a "delayed" DSN NOT be issued under any conditions.

The actual rules governing interpretation of the NOTIFY parameter are

given in section 6.

For compatibility with SMTP clients that do not use the NOTIFY

facility, the absence of a NOTIFY parameter in a RCPT command may be

interpreted as either NOTIFY=FAILURE or NOTIFY=FAILURE,DELAY.

5.2 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.

The ABNF for the ORCPT parameter is:

orcpt-parameter = "ORCPT=" original-recipient-address

original-recipient-address = addr-type ";" xtext

addr-type = atom

The "addr-type" portion MUST be an IANA-registered electronic mail

address-type (as defined in [5]), while the "xtext" portion contains

an encoded representation of the original recipient address using the

rules in section 5 of this document. The entire ORCPT parameter MAY

be up to 500 characters in length.

When initially submitting a message via SMTP, if the ORCPT parameter

is used, it MUST contain the same address as the RCPT TO address

(unlike the RCPT TO address, the ORCPT parameter will be encoded as

xtext). Likewise, when a mailing list submits a message via SMTP to

be distributed to the list subscribers, if ORCPT is used, the ORCPT

parameter MUST match the new RCPT TO address of each recipient, not

the address specified by the original sender of the message.)

The "addr-type" portion of the original-recipient-address is used to

indicate the "type" of the address which appears in the ORCPT

parameter value. However, the address associated with the ORCPT

keyword is NOT constrained to conform to the syntax rules for that

"addr-type".

Ideally, the "xtext" portion of the original-recipient-address 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

representation of recipient address must be defined by a

specification for gatewaying between DSNs and that environment.

5.3 The RET parameter of the ESMTP MAIL command

The RET esmtp-keyword on the extended MAIL command specifies whether

or not the message should be included in any failed DSN issued for

this message transmission. If the RET esmtp-keyword is used, it MUST

have an associated esmtp-value, which is one of the following

keywords:

FULL requests that the entire message be returned in any "failed"

delivery status notification issued for this recipient.

HDRS requests that only the headers of the message be returned.

The FULL and HDRS keywords may be spelled in any combination of upper

and lower case letters.

If no RET parameter is supplied, the MTA MAY return either the

headers of the message or the entire message for any DSN containing

indication of failed deliveries.

Note that the RET parameter only applies to DSNs that indicate

delivery failure for at least one recipient. If a DSN contains no

indications of delivery failure, only the headers of the message

should be returned.

5.4 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 ABNF for the ENVID parameter is:

envid-parameter = "ENVID=" xtext

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. The

ENVID parameter MAY be up to 100 characters in length.

5.5 Restrictions on the use of Delivery Status Notification parameters

The RET and ENVID parameters MUST NOT appear more than once each in

any 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".

The NOTIFY and ORCPT parameters MUST NOT appear more than once in any

RCPT command. If more than one of either of these parameters appears

in a RCPT command, the ESMTP server SHOULD respond with "501 syntax

error in parameters or arguments".

6. Conformance requirements

The Simple Mail Transfer Protocol (SMTP) is used by Message Transfer

Agents (MTAs) when accepting, relaying, or gatewaying mail, as well

as User Agents (UAs) when submitting mail to the mail transport

system. The DSN extension to SMTP may be used to allow UAs to convey

the sender's requests as to when DSNs should be issued. A UA which

claims to conform to this specification must meet certain

requirements as described below.

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, when acting as an SMTP server, issues the DSN keyword in

response to the EHLO command, MUST obey the rules below for a

"conforming SMTP client" when acting as a client, and a "conforming

SMTP server" when acting as a server. The term "conforming MTA"

refers to an MTA which conforms to this specification, independent of

its role of client or server.

6.1 SMTP protocol interactions

The following rules apply to SMTP transactions in which any of the

ENVID, NOTIFY, RET, or ORCPT keywords are used:

(a) If an SMTP client issues a MAIL command containing a valid ENVID

parameter and associated esmtp-value and/or a valid RET parameter

and associated esmtp-value, a conforming SMTP server MUST return

the same reply-code as it would to the same MAIL command without

the ENVID and/or RET parameters. A conforming SMTP server MUST

NOT refuse a MAIL command based on the absence or presence of

valid ENVID or RET parameters, or on their associated

esmtp-values.

However, if the associated esmtp-value is not valid (i.e. contains

illegal characters), or if there is more than one ENVID or RET

parameter in a particular MAIL command, the server MUST issue the

reply-code 501 with an appropriate message (e.g. "syntax error in

parameter").

(b) If an SMTP client issues a RCPT command containing any valid

NOTIFY and/or ORCPT parameters, a conforming SMTP server MUST

return the same response as it would to the same RCPT command

without those NOTIFY and/or ORCPT parameters. A conforming SMTP

server MUST NOT refuse a RCPT command based on the presence or

absence of any of these parameters.

However, if any of the associated esmtp-values 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".

6.2 Handling of messages received via SMTP

This section describes how a conforming MTA should handle any

messages received via SMTP.

NOTE: A DSN MUST NOT be returned to the sender for any message for

which the return address from the SMTP MAIL command was NULL ("<>"),

even if the sender's address is available from other sources (e.g.

the message header). However, the MTA which would otherwise issue a

DSN SHOULD inform the local postmaster of delivery failures through

some appropriate mechanism that will not itself result in the

generation of DSNs.

DISCUSSION: RFC1123, section 2.3.3 requires error notifications to

be sent with a NULL return address ("reverse-path"). This creates an

interesting situation when a message arrives with one or more

nonfunctional recipient addresses in addition to a nonfunctional

return address. When delivery to one of the recipient addresses

fails, the MTA will attempt to send a nondelivery notification to the

return address, setting the return address on the notification to

NULL. When the delivery of this notification fails, the MTA

attempting delivery of that notification sees a NULL return address.

If that MTA were not to inform anyone of the situation, the original

message would be silently lost. Furthermore, a nonfunctional return

address is often indicative of a configuration problem in the

sender's MTA. Reporting the condition to the local postmaster may

help to speed correction of such errors.

6.2.1 Relay of messages to other conforming SMTP servers

The following rules govern the behavior of a conforming MTA, when

relaying a message which was received via the SMTP protocol, to an

SMTP server that supports the Delivery Status Notification service

extension:

(a) 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, the ENVID parameter MUST NOT be supplied when the

message is relayed.

(b) Any RET 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 RET

parameter was included in the MAIL command when the message was

received, the RET parameter MUST NOT supplied when the message is

relayed.

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 the NOTIFY parameter was not supplied

for a recipient when the message was received, the NOTIFY parameter

MUST NOT be supplied for that recipient when the message is relayed.

(d) If any ORCPT parameter was present in the RCPT command for a

recipient when the message was received, an ORCPT parameter with the

identical original-recipient-address MUST appear in the RCPT command

issued for that recipient when relaying the message. (For example,

the MTA therefore MUST NOT change the case of any alphabetic

characters in an ORCPT parameter.)

If no ORCPT parameter was present in the RCPT command when the

message was received, an ORCPT parameter MAY be added to the RCPT

command when the message is relayed. If an ORCPT parameter is added

by the relaying MTA, it MUST contain the recipient address from the

RCPT command used when the message was received by that MTA.

6.2.2 Relay of messages to non-conforming SMTP servers

The following rules govern the behavior of a conforming MTA (in the

role of 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:

(a) ENVID, NOTIFY, RET, or ORCPT parameters MUST NOT be issued when

relaying the message.

(b) 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.

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.

(d) If the NOTIFY parameter was supplied for a recipient with an esmtp-

value of NEVER, the client MUST NOT issue a DSN for that recipient,

regardless of the reply-code returned by the SMTP server. However,

if the server returned a failure (5xx) reply-code, the client MAY

inform the local postmaster of the delivery failure via an

appropriate mechanism that will not itself result in the generation

of DSNs.

When attempting to relay a message to an SMTP server that does not

support this extension, and if NOTIFY=NEVER was specified for some

recipients of that message, a conforming SMTP client MAY relay the

message for those recipients in a separate SMTP transaction, using

an empty reverse-path in the MAIL command. This will prevent DSNs

from being issued for those recipients by MTAs that conform to [1].

(e) 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.

(f) 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.

6.2.3 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:

"Delivery" means that the message has been placed in the recipient's

mailbox. For messages which are transmitted to a mailbox for later

retrieval via IMAP [6], POP [7] or a similar message Access protocol,

"delivery" occurs when the message is made available to the IMAP

(POP, etc.) service, rather than when the message is retrieved by the

recipient's user agent.

Similarly, for a recipient address which corresponds to a mailing

list exploder, "delivery" occurs when the message is made available

to that list exploder, even though the list exploder might refuse to

deliver that message to the list recipients.

(a) 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.

(b) If the NOTIFY parameter was supplied for that recipient which did

not contain the SUCCESS keyword, the MTA MUST NOT issue a DSN for

that recipient.

MUST NOT issue a DSN.

6.2.4 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:

(a) 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.

(b) If a NOTIFY parameter was supplied with the SUCCESS keyword, but the

destination environment cannot return an appropriate notification on

successful delivery, the MTA SHOULD issue a "relayed" DSN for that

recipient.

DSN MUST NOT be issued. If possible, the MTA SHOULD direct the

destination environment to not issue delivery notifications for that

recipient.

(d) If the NOTIFY parameter was not supplied for a particular recipient,

a DSN SHOULD NOT be issued by the gateway. The gateway SHOULD

attempt to ensure that appropriate notification will be provided by

the foreign mail environment if eventual delivery failure occurs,

and that no notification will be issued on successful delivery.

(e) 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.

6.2.5 Delays in delivery

If a conforming MTA receives a message via the SMTP protocol, and is

unable to deliver or relay the message to one or more recipients for

an extended length of time (to be determined by the MTA), it MAY

issue a "delayed" DSN for those recipients, subject to the following

conditions:

(a) If the NOTIFY parameter was supplied for a recipient and its value

included the DELAY keyword, a "delayed" DSN MAY be issued.

(b) If the NOTIFY parameter was not supplied for a recipient, a

"delayed" DSN MAY be issued.

keyword, a "delayed" DSN MUST NOT be issued.

NOTE: Although delay notifications are common in present-day

electronic mail, 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.

6.2.6 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:

(a) If a NOTIFY parameter was supplied for the recipient with an esmtp-

keyword containing the value FAILURE, a "failed" DSN MUST be issued

by the MTA.

(b) If a NOTIFY parameter was supplied for the recipient which did not

contain the value FAILURE, a DSN MUST NOT be issued for that

recipient. However, the MTA MAY inform the local postmaster of the

delivery failure via some appropriate mechanism which does not

itself result in the generation of DSNs.

DSN MUST be issued.

NOTE: Some MTAs are known to forward undeliverable messages to the

local postmaster or "dead letter" mailbox. This is still considered

delivery failure, and does not diminish the requirement to issue a

"failed" DSN under the conditions defined elsewhere in this memo. If

a DSN is issued for such a recipient, the Action value MUST be

"failed".

6.2.7 Forwarding, aliases, and mailing lists

Delivery of a message to a local email address usually causes the

message to be stored in the recipient's mailbox. However, MTAs

commonly provide a facility where a local email address can be

designated as an "alias" or "mailing list"; delivery to that address

then causes the message to be forwarded to each of the (local or

remote) recipient addresses associated with the alias or list. It is

also common to allow a user to optionally "forward" her mail to one

or more alternate addresses. If this feature is enabled, her mail is

redistributed to those addresses instead of being deposited in her

mailbox.

Following the example of [9] (section 5.3.6), this document defines

the difference between an "alias" and "mailing list" as follows: When

forwarding a message to the addresses associated with an "alias", the

envelope return address (e.g. SMTP MAIL FROM) remains intact.

However, when forwarding a message to the addresses associated with a

"mailing list", the envelope return address is changed to that of the

administrator of the mailing list. This causes DSNs and other

nondelivery reports resulting from delivery to the list members to be

sent to the list administrator rather than the sender of the original

message.

The DSN processing for aliases and mailing lists is as follows:

6.2.7.1 mailing lists

When a message is delivered to a list submission address (i.e. placed

in the list's mailbox for incoming mail, or accepted by the process

that redistributes the message to the list subscribers), this is

considered final delivery for the original message. If the NOTIFY

parameter for the list submission address contained the SUCCESS

keyword, a "delivered" DSN MUST be returned to the sender of the

original message.

NOTE: Some mailing lists are able to reject message submissions,

based on the content of the message, the sender's address, or some

other criteria. While the interface between such a mailing list and

its MTA is not well-defined, it is important that DSNs NOT be issued

by both the MTA (to report successful delivery to the list), and the

list (to report message rejection using a "failure" DSN.)

However, even if a "delivered" DSN was issued by the MTA, a mailing

list which rejects a message submission MAY notify the sender that

the message was rejected using an ordinary message instead of a DSN.

Whenever a message is redistributed to an mailing list,

(a) The envelope return address is rewritten to point to the list

maintainer. This address MAY be that of a process that recognizes

DSNs and processes them automatically, but it MUST forward

unrecognized messages to the human responsible for the list.

(b) The ENVID, NOTIFY, RET, and ORCPT parameters which accompany the

redistributed message MUST NOT be derived from those of the original

message.

postmaster or the list administrator. If ORCPT parameters are

supplied during redistribution to the list subscribers, they SHOULD

contain the addresses of the list subscribers in the format used by

the mailing list.

6.2.7.2 single-recipient aliases

Under normal circumstances, when a message arrives for an "alias"

which has a single forwarding address, a DSN SHOULD NOT be issued.

Any ENVID, NOTIFY, RET, or ORCPT parameters SHOULD be propagated with

the message as it is redistributed to the forwarding address.

6.2.7.3 multiple-recipient aliases

An "alias" with multiple recipient addresses may be handled in any of

the following ways:

(a) Any ENVID, NOTIFY, RET, or ORCPT parameters are NOT propagated when

relaying the message to any of the forwarding addresses. If the

NOTIFY parameter for the alias contained the SUCCESS keyword, the

MTA issues a "relayed" DSN. (In effect, the MTA treats the message

as if it were being relayed into an environment that does not

support DSNs.)

(b) Any ENVID, NOTIFY, RET, or ORCPT parameters (or the equivalent

requests if the message is gatewayed) are propagated to EXACTLY one

of the forwarding addresses. No DSN is issued. (This is

appropriate when aliasing is used to forward a message to a

"vacation" auto-responder program in addition to the local mailbox.)

addresses associated with that alias. The NOTIFY parameter is

propagated to the forwarding addresses, except that it any SUCCESS

keyword is removed. If the original NOTIFY parameter for the alias

contained the SUCCESS keyword, an "expanded" DSN is issued for the

alias. If the NOTIFY parameter for the alias did not contain the

SUCCESS keyword, no DSN is issued for the alias.

6.2.7.4 confidential forwarding addresses

If it is desired to maintain the confidentiality of a recipient's

forwarding address, the forwarding may be treated as if it were a

mailing list. A DSN will be issued, if appropriate, upon "delivery"

to the recipient address specified by the sender. When the message

is forwarded it will have a new envelope return address. Any DSNs

which result from delivery failure of the forwarded message will not

be returned to the original sender of the message and thus not expose

the recipient's forwarding address.

6.2.8 DSNs describing delivery to multiple recipients

A single DSN may describe attempts to deliver a message to multiple

recipients of that message. If a DSN is issued for some recipients

in an SMTP transaction and not for others according to the rules

above, the DSN SHOULD NOT contain information for recipients for whom

DSNs would not otherwise have been issued.

6.3 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 message 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.

6.4 Implementation limits

A conforming MTA MUST accept ESMTP parameters of at least the

following sizes:

(a) ENVID parameter: 100 characters.

(b) NOTIFY parameter: 28 characters.

(d) RET parameter: 8 characters.

The maximum sizes for the ENVID and ORCPT parameters are intended to

be adequate for the transmission of "foreign" envelope identifier and

original recipient addresses. However, user agents which use SMTP as

a message submission protocol SHOULD NOT generate ENVID parameters

which are longer than 38 characters in length.

A conforming MTA MUST be able to accept SMTP command-lines which are

at least 1036 characters long (530 characters for the ORCPT and

NOTIFY parameters of the RCPT command, in addition to the 512

characters required by [1]). If other SMTP extensions are supported

by the MTA, the MTA MUST be able to accept a command-line large

enough for each SMTP command and any combination of ESMTP parameters

which may be used with that command.

7. Format of delivery notifications

The format of delivery status notifications is defined in [5], which

uses the framework defined in [8]. Delivery status notifications are

to be returned to the sender of the original message as outlined

below.

7.1 SMTP Envelope to be used with delivery status notifications

The DSN sender address (in the SMTP MAIL command) MUST be a null

reverse-path ("<>"), as required by section 5.3.3 of [9]. The DSN

recipient address (in the RCPT command) is copied from the MAIL

command which accompanied the message for which the DSN is being

issued. When transmitting a DSN via SMTP, the RET parameter MUST NOT

be used. The NOTIFY parameter MAY be used, but its value MUST be

NEVER. The ENVID parameter (with a newly generated envelope-id)

and/or ORCPT parameter MAY be used.

7.2 Contents of the DSN

A DSN is transmitted as a MIME message with a top-level content-type

of multipart/report (as defined in [5]).

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 is "delivery-status".

As described in [8], 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 original message or some portion

thereof. When the value of the RET parameter is FULL, the full

message SHOULD be returned for any DSN which conveys notification of

delivery failure. (However, if the length of the message is greater

than some implementation-specified length, the MTA MAY return only

the headers even if the RET parameter specified FULL.) If a DSN

contains no notifications of delivery failure, the MTA SHOULD return

only the headers.

The third component must have an appropriate content-type label.

Issues concerning selection of the content-type are discussed in [8].

7.3 Message/delivery-status fields

The message/delivery-status content-type defines a number of fields,

with general specifications for their contents. The following

requirements for any DSNs generated in response to a message received

by the SMTP protocol by a conforming SMTP server, are in addition to

the requirements defined in [5] for the message/delivery-status type.

When generating a DSN for a message which was received via the SMTP

protocol, a conforming MTA will generate the following fields of the

message/delivery-status body part:

(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. If the message was

received via SMTP with no ENVID parameter, the Original-Envelope-ID

field MUST NOT be supplied.

Since the ENVID parameter is encoded as xtext, but the Original-

Envelope-ID header is NOT encoded as xtext, the MTA must decode the

xtext encoding when copying the ENVID value to the Original-

Envelope-ID field.

(b) The Reporting-MTA field MUST be supplied. If Reporting MTA can

determine its fully-qualified Internet domain name, the MTA-name-

type subfield MUST be "dns", and the field MUST contain the fully-

qualified domain name of the Reporting MTA. If the fully-qualified

Internet domain name of the Reporting MTA is not known (for example,

for an SMTP server which is not directly connected to the Internet),

the Reporting-MTA field may contain any string identifying the MTA,

however, in this case the MTA-name-type subfield MUST NOT be "dns".

A MTA-name-type subfield value of "x-local-hostname" is suggested.

appropriate.

(d) If the ORCPT parameter was provided for this recipient, the

Original-Recipient field MUST be supplied, with its value taken from

the ORCPT parameter. If no ORCPT parameter was provided for this

recipient, the Original-Recipient field MUST NOT appear.

(e) The Final-Recipient field MUST be supplied. It MUST contain the

recipient address from the message envelope. If the message was

received via SMTP, the address-type will be "rfc822".

(f) The Action field MUST be supplied.

(g) The Status field MUST be supplied, using a status-code from [10].

If there is no specific code which suitably describes a delivery

failure, either 4.0.0 (temporary failure), or 5.0.0 (permanent

failure) MUST be used.

(h) For DSNs resulting from attempts to relay a message to one or more

recipients via SMTP, the Remote-MTA field MUST be supplied for each

of those recipients. The mta-name-type subfields of those Remote-

MTA fields will be "dns".

(i) For DSNs resulting from attempts to relay a message to one or more

recipients via SMTP, the Diagnostic-Code MUST be supplied for each

of those recipients. The diagnostic-type subfield will be "smtp".

See section 9.2(a) of this document for a description of the "smtp"

diagnostic-code.

(j) For DSNs resulting from attempts to relay a message to one or more

recipients via SMTP, an SMTP-Remote-Recipient extension field MAY be

supplied for each recipient, which contains the address of that

recpient which was presented to the remote SMTP server.

(k) Other per-recipient fields defined in [5] MAY appear, as

appropriate.

8. Acknowledgments

The author wishes to thank Eric Allman, Harald Alvestrand, Jim

Conklin, Bryan Costales, Peter Cowen, Dave Crocker, Roger Fajman, Ned

Freed, Marko Kaittola, Steve Kille, John Klensin, Anastasios

Kotsikonas, John Gardiner Myers, Julian Onions, Jacob Palme, Marshall

Rose, Greg Vaudreuil, and Klaus Weide for their suggestions for

improvement of this document.

9. Appendix - Type-Name Definitions

The following type names are defined for use in DSN fields generated

by conforming SMTP-based MTAs:

9.1 "rfc822" address-type

The "rfc822" address-type is to be used when reporting Internet

electronic mail address in the Original-Recipient and Final-Recipient

DSN fields.

(a) address-type name: rfc822

(b) syntax for mailbox addresses

RFC822 mailbox addresses are generally expected to be of the form

[route] addr-spec

where "route" and "addr-spec" are defined in [2], and the "domain"

portions of both "route" and "addr-spec" are fully-qualified domain

names that are registered in the DNS. However, an MTA MUST NOT

modify an address oBTained from the message envelope to force it to

conform to syntax rules.

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.

RFC822 addresses consist entirely of graphic characters from the US-

ASCII repertoire, so no translation is necessary.

9.2 "smtp" diagnostic-type

The "smtp" diagnostic-type is to be used when reporting SMTP reply-

codes in Diagnostic-Code DSN fields.

(a) diagnostic-type name: SMTP

(b) A description of the syntax to be used for expressing diagnostic

codes of this type as graphic characters from the US-ASCII repertoire.

An SMTP diagnostic-code is of the form

*( 3*DIGIT "-" *text ) 3*DIGIT SPACE *text

For a single-line SMTP reply to an SMTP command, the diagnostic-code

SHOULD be an exact transcription of the reply. For multi-line SMTP

replies, it is necessary to insert a SPACE before each line after

the first. For example, an SMTP reply of:

550-mailbox unavailable

550 user has moved with no forwarding address

could appear as follows in a Diagnostic-Code DSN field:

Diagnostic-Code: smtp ; 550-mailbox unavailable

550 user has moved with no forwarding address

each code.

SMTP reply-codes are currently defined in [1], [4], and [9].

Additional codes may be defined by other RFCs.

9.3 "dns" MTA-name-type

The "dns" MTA-name-type should be used in the Reporting-MTA field.

An MTA-name of type "dns" is a fully-qualified domain name. The name

must be registered in the DNS, and the address Postmaster@{mta-name}

must be valid.

(a) MTA-name-type name: dns

(b) A description of the syntax of MTA names of this type, using BNF,

regular expressions, ASN.1, or other non-ambiguous language.

MTA names of type "dns" SHOULD be valid Internet domain names. If

such domain names are not available, a domain-literal containing the

internet protocol address is acceptable. Such domain names

generally conform to the following syntax:

domain = real-domain / domain-literal

real-domain = sub-domain *("." sub-domain)

sub-domain = atom

domain-literal = "[" 1*3DIGIT 3("." 1*3DIGIT) "]"

where "atom" and "DIGIT" are defined in [2].

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.

MTA names of type "dns" consist entirely of graphic US-ASCII

characters, so no translation is needed.

10. Appendix - Example

This example traces the flow of a single message addressed to

multiple recipients. The message is sent by Alice@Pure-Heart.ORG to

Bob@Big-Bucks.COM, Carol@Ivory.EDU, Dana@Ivory.EDU,

Eric@Bombs.AF.MIL, Fred@Bombs.AF.MIL, and George@Tax-ME.GOV, with a

variety of per-recipient options. The message is successfully

delivered to Bob, Dana (via a gateway), Eric, and Fred. Delivery

fails for Carol and George.

NOTE: Formatting rules for RFCs require that no line be longer than

72 characters. Therefore, in the following examples, some SMTP

commands longer than 72 characters are printed on two lines, with the

first line ending in "\". In an actual SMTP transaction, such a

command would be sent as a single line (i.e. with no embedded CRLFs),

and without the "\" character that appears in these examples.

10.1 Submission

Alice's user agent sends the message to the SMTP server at Pure-

Heart.ORG. Note that while this example uses SMTP as a mail

submission protocol, other protocols could also be used.

<<< 220 Pure-Heart.ORG SMTP server here

>>> EHLO Pure-Heart.ORG

<<< 250-Pure-Heart.ORG

<<< 250-DSN

<<< 250-EXPN

<<< 250 SIZE

>>> MAIL FROM:<Alice@Pure-Heart.ORG> RET=HDRS ENVID=QQ314159

<<< 250 <Alice@Pure-Heart.ORG> sender ok

>>> RCPT TO:<Bob@Big-Bucks.COM> NOTIFY=SUCCESS ORCPT=rfc822;Bob@Big-Bucks.COM

<<< 250 <Bob@Big-Bucks.COM> recipient ok

>>> RCPT TO:<Carol@Ivory.EDU> NOTIFY=FAILURE ORCPT=rfc822;Carol@Ivory.EDU

<<< 250 <Carol@Ivory.EDU> recipient ok

>>> RCPT TO:<Dana@Ivory.EDU> NOTIFY=SUCCESS,FAILURE ORCPT=rfc822;Dana@Ivory.EDU

<<< 250 <Dana@Ivory.EDU> recipient ok

>>> RCPT TO:<Eric@Bombs.AF.MIL> NOTIFY=FAILURE ORCPT=rfc822;Eric@Bombs.AF.MIL

<<< 250 <Eric@Bombs.AF.MIL> recipient ok

>>> RCPT TO:<Fred@Bombs.AF.MIL> NOTIFY=NEVER

<<< 250 <Fred@Bombs.AF.MIL> recipient ok

>>> RCPT TO:<George@Tax-ME.GOV> NOTIFY=FAILURE ORCPT=rfc822;George@Tax-ME.GOV

<<< 250 <George@Tax-ME.GOV> recipient ok

>>> DATA

<<< 354 okay, send message

>>> (message goes here)

>>> .

<<< 250 message accepted

>>> QUIT

<<< 221 goodbye

10.2 Relay to Big-Bucks.COM

The SMTP at Pure-Heart.ORG then relays the message to Big-Bucks.COM.

(For the purpose of this example, mail.Big-Bucks.COM is the primary

mail exchanger for Big-Bucks.COM).

<<< 220 mail.Big-Bucks.COM says hello

>>> EHLO Pure-Heart.ORG

<<< 250-mail.Big-Bucks.COM

<<< 250 DSN

>>> MAIL FROM:<Alice@Pure-Heart.ORG> RET=HDRS ENVID=QQ314159

<<< 250 sender okay

>>> RCPT TO:<Bob@Big-Bucks.COM> NOTIFY=SUCCESS ORCPT=rfc822;Bob@Big-Bucks.COM

<<< 250 recipient okay

>>> DATA

<<< 354 send message

>>> (message goes here)

>>> .

<<< 250 message received

>>> QUIT

<<< 221 bcnu

10.3 Relay to Ivory.EDU

The SMTP at Pure-Heart.ORG relays the message to Ivory.EDU, which (as

it happens) is a gateway to a LAN-based mail system that accepts SMTP

mail and supports the DSN extension.

<<< 220 Ivory.EDU gateway to FooMail(tm) here

>>> EHLO Pure-Heart.ORG

<<< 250-Ivory.EDU

<<< 250 DSN

>>> MAIL FROM:<Alice@Pure-Heart.ORG> RET=HDRS ENVID=QQ314159

<<< 250 ok

>>> RCPT TO:<Carol@Ivory.EDU> NOTIFY=FAILURE ORCPT=rfc822;Carol@Ivory.EDU

<<< 550 error - no such recipient

>>> RCPT TO:<Dana@Ivory.EDU> NOTIFY=SUCCESS,FAILURE ORCPT=rfc822;Dana@Ivory.EDU

<<< 250 recipient ok

>>> DATA

<<< 354 send message, end with '.'

>>> (message goes here)

>>> .

<<< 250 message received

>>> QUIT

<<< 221 bye

Note that since the Ivory.EDU refused to accept mail for

Carol@Ivory.EDU, and the sender specified NOTIFY=FAILURE, the

sender-SMTP (in this case Pure-Heart.ORG) must generate a DSN.

10.4 Relay to Bombs.AF.MIL

The SMTP at Pure-Heart.ORG relays the message to Bombs.AF.MIL, which

does not support the SMTP extension. Because the sender specified

NOTIFY=NEVER for recipient Fred@Bombs.AF.MIL, the SMTP at Pure-

Heart.ORG chooses to send the message for that recipient in a

separate transaction with a reverse-path of <>.

<<< 220-Bombs.AF.MIL reporting for duty.

<<< 220 Electronic mail is to be used for official business only.

>>> EHLO Pure-Heart.ORG

<<< 502 command not implemented

>>> RSET

<<< 250 reset

>>> HELO Pure-Heart.ORG

<<< 250 Bombs.AF.MIL

>>> MAIL FROM:<Alice@Pure-Heart.ORG>

<<< 250 ok

>>> RCPT TO:<Eric@Bombs.AF.MIL>

<<< 250 ok

>>> DATA

<<< 354 send message

>>> (message goes here)

>>> .

<<< 250 message accepted

>>> MAIL FROM:<>

<<< 250 ok

>>> RCPT TO:<Fred@Bombs.AF.MIL>

<<< 250 ok

>>> DATA

<<< 354 send message

>>> (message goes here)

>>> .

<<< 250 message accepted

>>> QUIT

<<< 221 Bombs.AF.MIL closing connection

10.5 Forward from George@Tax-ME.GOV to Sam@Boondoggle.GOV

The SMTP at Pure-Heart.ORG relays the message to Tax-ME.GOV. (this

step is not shown). MTA Tax-ME.GOV then forwards the message to

Sam@Boondoggle.GOV (shown below). Both Tax-ME.GOV and Pure-Heart.ORG

support the SMTP DSN extension. Note that RET, ENVID, and ORCPT all

retain their original values.

<<< 220 BoonDoggle.GOV says hello

>>> EHLO Pure-Heart.ORG

<<< 250-mail.Big-Bucks.COM

<<< 250 DSN

>>> MAIL FROM:<Alice@Pure-Heart.ORG> RET=HDRS ENVID=QQ314159

<<< 250 sender okay

>>> RCPT TO:<Sam@Boondoggle.GOV> NOTIFY=SUCCESS ORCPT=rfc822;George@Tax-ME.GOV

<<< 250 recipient okay

>>> DATA

<<< 354 send message

>>> (message goes here)

>>> .

<<< 250 message received

>>> QUIT

<<< 221 bcnu

10.6 "Delivered" DSN for Bob@Big-Bucks.COM

MTA mail.Big-Bucks.COM successfully delivers the message to Bob@Big-

Bucks.COM. Because the sender specified NOTIFY=SUCCESS, mail.Big-

Bucks.COM issues the following DSN, and sends it to Alice@Pure-

Heart.ORG.

To: Alice@Pure-Heart.ORG

From: postmaster@mail.Big-Bucks.COM

Subject: Delivery Notification (success) for Bob@Big-Bucks.COM

Content-Type: multipart/report; report-type=delivery-status;

boundary=abcde

MIME-Version: 1.0

--abcde

Content-type: text/plain; charset=us-ascii

Your message (id QQ314159) was successfully delivered to

Bob@Big-Bucks.COM.

--abcde

Content-type: message/delivery-status

Reporting-MTA: dns; mail.Big-Bucks.COM

Original-Envelope-ID: QQ314159

Original-Recipient: rfc822;Bob@Big-Bucks.COM

Final-Recipient: rfc822;Bob@Big-Bucks.COM

Action: delivered

Status: 2.0.0

--abcde

Content-type: message/rfc822

(headers of returned message go here)

--abcde--

10.7 Failed DSN for Carol@Ivory.EDU

Because delivery to Carol failed and the sender specified

NOTIFY=FAILURE for Carol@Ivory.EDU, MTA Pure-Heart.ORG (the SMTP

client to which the failure was reported via SMTP) issues the

following DSN.

To: Alice@Pure-Heart.ORG

From: postmaster@Pure-Heart.ORG

Subject: Delivery Notification (failure) for Carol@Ivory.EDU

Content-Type: multipart/report; report-type=delivery-status;

boundary=bcdef

MIME-Version: 1.0

--bcdef

Content-type: text/plain; charset=us-ascii

Your message (id QQ314159) could not be delivered to

Carol@Ivory.EDU.

A transcript of the session follows:

(while talking to Ivory.EDU)

>>> RCPT TO:<Carol@Ivory.EDU> NOTIFY=FAILURE

<<< 550 error - no such recipient

--bcdef

Content-type: message/delivery-status

Reporting-MTA: dns; Pure-Heart.ORG

Original-Envelope-ID: QQ314159

Original-Recipient: rfc822;Carol@Ivory.EDU

Final-Recipient: rfc822;Carol@Ivory.EDU

SMTP-Remote-Recipient: Carol@Ivory.EDU

Diagnostic-Code: smtp; 550 error - no such recipient

Action: failed

Status: 5.0.0

--bcdef

Content-type: message/rfc822

(headers of returned message go here)

--bcdef--

10.8 Relayed DSN For Dana@Ivory.EDU

Although the mail gateway Ivory.EDU supports the DSN SMTP extension,

the LAN mail system attached to its other side does not generate

positive delivery confirmations. So Ivory.EDU issues a "relayed"

DSN:

To: Alice@Pure-Heart.ORG

From: postmaster@Ivory.EDU

Subject: mail relayed for Dana@Ivory.EDU

Content-Type: multipart/report; report-type=delivery-status;

boundary=cdefg

MIME-Version: 1.0

--cdefg

Content-type: text/plain; charset=us-ascii

Your message (addressed to Dana@Ivory.EDU) was successfully

relayed to:

ymail!Dana

by the FooMail gateway at Ivory.EDU.

Unfortunately, the remote mail system does not support

confirmation of actual delivery. Unless delivery to ymail!Dana

fails, this will be the only delivery status notification sent.

--cdefg

Content-type: message/delivery-status

Reporting-MTA: dns; Ivory.EDU

Original-Envelope-ID: QQ314159

Original-Recipient: rfc822;Dana@Ivory.EDU

Final-Recipient: rfc822;Dana@Ivory.EDU

Action: relayed

Status: 2.0.0

--cdefg

Content-type: message/rfc822

(headers of returned message go here)

--cdefg--

10.9 Failure notification for Sam@Boondoggle.GOV

The message originally addressed to George@Tax-ME.GOV was forwarded

to Sam@Boondoggle.GOV, but the MTA for Boondoggle.GOV was unable to

deliver the message due to a lack of disk space in Sam's mailbox.

After trying for several days, Boondoggle.GOV returned the following

DSN:

To: Alice@BigHeart.ORG

From: Postmaster@Boondoggle.GOV

Subject: Delivery failure for Sam@Boondoggle.GOV

Content-Type: multipart/report; report-type=delivery-status;

boundary=defgh

MIME-Version: 1.0

--defgh

Your message, originally addressed to George@Tax-ME.GOV, and forwarded

from there to Sam@Boondoggle.GOV could not be delivered, for the

following reason:

write error to mailbox, disk quota exceeded

--defgh

Content-type: message/delivery-status

Reporting-MTA: Boondoggle.GOV

Original-Envelope-ID: QQ314159

Original-Recipient: rfc822;George@Tax-ME.GOV

Final-Recipient: rfc822;Sam@Boondoggle.GOV

Action: failed

Status: 4.2.2 (disk quota exceeded)

--defgh

Content-type: message/rfc822

(headers of returned message go here)

--defgh--

11. References

[1] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC821,

USC/Information Sciences Institute, August 1982.

[2] Crocker, D., "Standard for the Format of ARPA Internet Text

Messages", STD 11, RFC822, UDEL, August 1982.

[3] Westine, A., and J. Postel, "Problems with the Maintenance of

Large Mailing Lists.", RFC1211, USC/Information Sciences

Institute, March 1991.

[4] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D. Crocker,

"SMTP Service Extensions", RFC1651, MCI, Innosoft, Dover Beach

Consulting, Inc., Network Management Associates, Inc., Silicon

Graphics, Inc., July 1994.

[5] Moore, K., and G. Vaudreuil, "An Extensible Message Format for

Delivery Status Notifications", RFC1894, University of Tennessee,

Octel Network Services, January 1996.

[6] Crispin, M., "Internet Message Access Protocol - Version 4", RFC

1730, University of Washington, 20 December 1994.

[7] Myers, J., and M. Rose, "Post Office Protocol - Version 3", RFC

1725, Carnegie Mellon, Dover Beach Consulting, November 1994.

[8] Vaudreuil, G., "The Multipart/Report Content Type for the

Reporting of Mail System Administrative Messages", RFC1892, Octel

Network Services, January 1996.

[9] Braden, R., Editor, "Requirements for Internet Hosts - Application

and Support", STD 3, RFC1123, IETF, October 1989.

[10] Vaudreuil, G., "Enhanced Mail System Status Codes", RFC1893,

Octel Network Services, January 1996.

12. Author's Address

Keith Moore

University of Tennessee

107 Ayres Hall

Knoxville, TN 37996-1301

USA