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Versions: 00 01 02 03 04 05 06 rfc2076                                  
Network Working Group                                       Jacob Palme
Internet Draft                                 Stockholm University/KTH
<draft-ietf-mailext-mail-attributes-01.txt>                      Sweden
Category: Informational                                       June 1995
Expires December 1995


                 Common Internet Message Attributes

                       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 inappropriate 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).

 This memo provides information for the Internet community. This'
 memo does not specify an Internet standard of any kind, since
 this document is mainly a compilation of information taken from
 other RFC-s.. Distribution of this memo is unlimited.

                           Abstract

This memo contains a table of commonly occurring attributes in
headings and on envelopes of e-mail messages. The document compiles
information from other RFC-s such as RFC 821, RFC 822, RFC 1036,
RFC 1327, RFC 1496, RFC 1521, RFC 1766 and X.400. A few commonly
occurring attributes which are not defined in RFC-s are also
included. For each attribute, the memo gives a short description
and a reference to the RFC or X.400 part, in which the attribute
is defined.









<mail-attributes-01.txt>   Common Internet Message Attributes   June 1994
Palme                                                            [Page 1]


                        Table of contents

4. Introduction
5. Use of gatewaying attributes
6. Table of attributes
  6.1  Addressing information
  6.2  Envelope and format information
  6.3  Header fields containing mailbox names and addressable entities
  6.4  Message identification and referral attributes
  6.5  Other textual attributes
  6.6  Attributes containing dates and times
  6.7  Attributes containing other types of information
  6.8  Resent-attributes
  6.9  Sometimes occurring heading fields in Internet mail
       which are not according to standard
7. Acknowledgments
8. References
9. Author's address
Appendix A: Attributes sorted by Internet RFC document in which
           they appear

                        1. Introduction

Many different Internet standards and RFC-s define attributes which
may occur on Internet Mail Messages and Network News Articles. The
intention of this document is to list all such attributes in one
document as an aid to people developing message systems or interested
in Internet Mail standards.

The document contains all heading attributes which the author has
found in the following Internet standards: RFC 821 [1], RFC 822 [2],
RFC 1036 [3], RFC 1327 [4], RFC 1496 [5], RFC 1521 [6] and
RFC 1766 [8]. Note in particular that heading attributes defined in
RFC 1421-1424, "Privacy Enhancement for Internet Electronic Mail",
are not included. A few additional attributes which often can be
found in e-mail headings are also included.

For each heading attribute, the document gives a short description and
a reference to the Internet standard or RFC, in which they are defined.
Information about corresponding attributes in X.400 is also given
when available.

                2. Use of gatewaying attributes

RFC 1327 defines a number of new attributes in Internet mail, which
are defined to map attributes which X.400 have but which were
previously not standardized in Internet mail. Some of these attributes
are obviously useful also as stand-alone Internet mail message
attributes. The fact that an attribute occurs in RFC 1327 indicates
that it is recommended for use in gatewaying messages between X.400




<mail-attributes-01.txt>   Common Internet Message Attributes   June 1994Palme                                                            [Page 1]


and Internet mail, but does not necessarily mean that the attribute
is recommended for messages wholly within Internet mail. However, some
of these attributes may eventually get accepted also for usage within
Internet mail.

Fields are given here in the spelling used in e-mail headers. This
may sometimes be English, sometimes American spelling. One attribute,
"Organisation/Organization" occurs in e-mail headers sometimes with
English, sometimes with American spelling.

                     3. Table of attributes

                   3.1 Addressing information

Description             Internet att- Internet     X.400        X400
                       ribute name   document     attribute    document
-----------------------+-------------+------------+------------+-------+

Original sender. Should MAIL FROM     RFC 821      Originator   X.411
in Internet be empty                               name
when sending
notifications, and be
the list administrator
when forwarding from a
distribution list.

Relative address to the Return-Path:  RFC 821      Trace        X.411
original sender along
the reverse path
through which the
message was sent

Recipient to which      RCPT TO       RFC 821      Recipient    X.411
message is to be                                   name
delivered.

                3.2 Envelope and format information

Description             Internet att- Internet     X.400        X400
                       ribute name   document     attribute    document
-----------------------+-------------+------------+------------+-------+

All that is inside the  DATA          RFC 821      Content      X.411
envelope.

Trace of MTA-s which a  Received:     RFC 822:     Trace        X.411
message has passed.                   4.3.2

MIME protocol version.  MIME-Version: RFC 1521: 3  Mapped into  RFC
                                                  body part    1496




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Format of content       Content-Type: RFC 1521: 4  Mapped into  RFC
(character set etc.)                               body part    1496

Coding method used in   Content-      RFC 1521: 5
content.                Transfer-
                       Encoding

List of MTA-s passed.   Path:         RFC 1036:    Trace        X.411
                                     2.1.6

Special Usenet News     Control:      RFC 1036:
actions.                              2.2.6

Trace of distribution   DL-Expansion- RFC 1327    DL Expansion  X.411
lists passed.           history-                  History
                       indication                indication

Which body part types   Original-     RFC 1327    Original-     X.411
occur in this message.  Encoded-                  encoded-
                       Information-              information-
                       Types:                    types

Special informational   Message-Type: RFC 1327    Notification  X.411
message.                Delivery
                       Report

Controls whether this   Alternate-    RFC 1327    Alternate-    X.411
message may be          recipient:                recipient-
forwarded to alternate                            allowed
recipiets such as a
postmaster if delivery
is not possible to the
intended recipient.
Default: Allowed.

Whether non-delivery    Prevent-      RFC 1327    Originator    X.411
report is wanted at     NonDelivery-              ReportRequest
delivery error. Default Report:
is to want such a
report.

Whether a delivery      Generate-     RFC 1327    Originator    X.411
report is wanted at     Delivery-                 ReportRequest
successful delivery.    Report:
Default is not to
generate such a report.

Whether recipients are  Disclose-     RFC 1327    Disclosure-   X.411
to be told the names of Recipients:               of-recipients
other recipients of the
same message. This is



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primarily an X.400
facility, such
disclosure is in
Internet mail done via
the To:, Cc: and Bcc:
heading fields.

Indicates whether the   Content-     RFC 1327    Content-return- X.411
content of a message is Return                   request
to be returned with
non-delivery
notifications.

 3.3 Header fields containing mailbox names and addressable entitities

Description             Internet att- Internet     X.400        X400
                       ribute name   document     attribute    document
-----------------------+-------------+------------+------------+-------+

Replacement for "From:" Reply-To:     RFC 822:     Reply-       X.420
to which replies are to 4.4.3                      recipients
be sent. Not to be used
as a replacement for
all recipients of a
reply to a multi-reci-
pient message.

Author, approver.       From:         RFC 822:     Authorizing- X.420
                                     4.4.1        users

Moderator.              Approved:     RFC 1036:    Authorizing- X.420
                                     2.2.11       users

Sender information      Sender:       RFC 822:     Originator   X.420
inside the envelope.                  4.4.2

Main recipients.        To:           RFC 822:     Primary-     X.420
                                     4.5.1        recipients

Additional recipients.  Cc:           RFC 822:     Copy-        X.420
                                     4.5.2        recipients

Recipients not shown to Bcc:          RFC 822:     Blind-copy-  X.420
other recipients.                     4.5.3        recipients

In Usenet News: group   Newsgroups:   RFC 1036:    Primary-     X.420
to which this article                 2.1.3        Recipient
was posted. In e-mail:
either group to which
this message was posted
or group to which the



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article this message is
a reply-to was posted.

Where group replies to  Followup-To:  RFC 1036:
this message are to be                2.2.3
sent.

Limitation on where     Distribution: RFC 1036:
this message can be                   2.2.7
distributed.

            3.4 Message identification and referral attributes

Description             Internet att- Internet     X.400        X400
                       ribute name   document     attribute    document
-----------------------+-------------+------------+------------+-------+

Unique ID of this       Message-ID:   RFC 822:     IPM          X.420
message.                              4.6.1        Identifier

Unique ID of one body   Content-ID:   RFC 1521:    not
part of the content of                6.1          available
a message.

Reference to message    In-Reply-To:  RFC 822:     Replied-to-  X.420
which this message is a               4.6.2        IPM
reply to.

Reference to other      References:   RFC 822:     Related-IPMs X.420
related messages.                     4.6.3

Reference to previous   Obsoletes:    RFC 1327     Obsoleting   X.420
message being corrected
and replaced.

                        3.5 Other textual attributes

Description             Internet att- Internet     X.400        X400
                       ribute name   document     attribute    document
-----------------------+-------------+------------+------------+-------+

Search keys for data    Keywords:      RFC 822:    Heading      RFC 1327
base retrieval.                        4.6.4       extension

Title, heading,         Subject:       RFC 822:    Subject      X.420
subject.                               4.7.1

Comments on a message.  Comments:      RFC 822:    Extra body   X.420
                                      4.7.2       part

Description of a        Content-       RFC 1521:   Heading      RFC 1327



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particular body part    description:   6.2         extension
of a message.

Organization to which   Organization:  RFC 1036:   organization- X.520
the sender of this                     2.2.8       name
message belongs.

Short text describing   Summary:      RFC 1036:    Heading      RFC 1327
a longer message.                     2.2.10       extension???

A text string which     Content-      RFC 1327     Content-     X.411
identifies the content  identifier:                identifier
of a message.

                   3.6 Attributes containing dates and times

Description             Internet att- Internet     X.400        X400
                       ribute name   document     attribute    document
-----------------------+-------------+------------+------------+-------+

The time when a         Delivery-     RFC 1327     Message-     X.411
message was delivered   Date:                      delivery
to its recipient.                                  time

In Internet, the date   Date:         RFC 822:     Message-     X.411
when a message was                    5.1          submission-
written, in X.400, the                             time
time a message was
submitted.

A suggested expiration  Expires:      RFC 1036:    Expiry Date  X.420
date. Can be used both                2.2.4        Indication
to limit the time of an
article which is not
meaningful after a
certain date, and to
extend the storage of
important articles.

Time at which a message Expiry-Date:  RFC 1327     Expiry Date  X.420
loses its validity.                                Indication

Latest time at which a  Reply-By:     RFC 1327     ReplyTime    X.420
reply is requested (not                            Field
demanded).

           3.7 Attributes containing other types of information

Description             Internet att- Internet     X.400        X400
                       ribute name   document     attribute    document
-----------------------+-------------+------------+------------+-------+



<mail-attributes-01.txt>   Common Internet Message Attributes   June 1994Palme                                                            [Page 1]


Can be normal, urgent   Priority:     RFC 1327     Priority     X.411
or non-urgent and can
influence transmission
speed and delivery.

Size of the message.    Lines:        RFC 1036:    Heading      RFC 1327
                                       2.2.12     extension???

Has been automatically  Auto-         RFC 1327     Auto-        X.420
forwarded.              Forwarded:                 Forwarded
                                                  Indication

Can be high, normal or  Importance:   RFC 1327     Importance   X.420
low and is only used in
the recipient client
(UA).

Body parts are missing. Incomplete-   RFC 1327     Incomplete   X.420
                       Copy:                      Copy

Can include a code      Language:     RFC 1766     Language     X.420
code for the natural                  RFC 1327
language used in a
message, e.g. "en"
for English.

Can be personal,        Sensitivity:  RFC 1327     Sensitivity  X.420
private, company-
confidential or
absent.

The body of this        Conversion:   RFC 1327     Implicit-    X.411
message may not be                                 conversion-
converted from one                                 prohibited
character set to
another.

The body of this        Conversion-   RFC 1327     Conversion-  X.411
message may not be      With-Loss:                 with-loss-
converted from one                                 prohibited
character set to
another if information
will be lost.

Can be used in Internet Discarded-    RFC 1327     Extensions   X.420
mail to indicate X.400  X400-IPMS-                 Field
extensions which        Extensions:
could not be mapped
to Internet mail        Discarded-    RFC 1327     Extensions   X.420
format.                 X400-MTS-                  Field



<mail-attributes-01.txt>   Common Internet Message Attributes   June 1994Palme                                                            [Page 1]


                       Extensions:

                        3.8 Resent-attributes

Description             Internet att- Internet     X.400        X400
                       ribute name   document     attribute    document
-----------------------+-------------+------------+------------+-------+

When forwarding a       Resent-Reply- RFC 822,     Embedded     X.420
message, attributes     To:, Resent-  C.3.3        message
referring to the        From:, Resent-             bodies
forwarding, not to the  Sender:,                   should be
original message.       Resent-From:,              used for
                       Resent-Date:,              forwarding.
Note: MIME specifies    Resent-To:,
another way of resen-   Resent-cc:,
ding messages, using    Resent-bcc:,
the "Message" Content-  Resent-
Type.                   Message-ID:

         3.9 Sometimes occurring heading fields in Internet mail
                  which are not according to standard

This chapter does not include a complete collection of all heading
attributes, such a list would be much longer. It contains a few
attributes which occur frequently and for which an explanation may be
useful here.

Description             Internet att- Internet     X.400        X400
                       ribute name   document     attribute    document
-----------------------+-------------+------------+------------+-------+

Inserted by Sendmail    Apparently-   RFC 1211
in certain cases, lis-  to:
ting recipients deriv-
ed from the envelope
into the message
heading. This behavi-
or is not quite pro-
per, MTA-s should not
modify headings (ex-
cept inserting Reci-
eved lines), and it
can in some cases
cause Bcc recipients
to be wrongly divulged.

Inserted by certain     Content-
mailers to indicate     length:
the size in bytes of
the message text. Can



<mail-attributes-01.txt>   Common Internet Message Attributes   June 1994Palme                                                            [Page 1]


cause several robust-
ness and interoperabi-
lity problems and is
not recommended.

Pre-MIME way of indi-   Encoding:     RFC 1154
cating encoding format
in message.

Address to which        Errors-To:,
notifications are to    Return-
be sent. Internet       Receipt-To:
standards recommend,
however, the use of
RCPT TO and Return-
Path, not Errors-To,
for this.

Fax number of the       Fax:,                      X.520
originator.             Telefax:

Name of file in which a Fcc:
copy of this message is
stored.

Information about the   Mail-System-
client software of the  Version:,
originator.             Mailer:

See Organization.       Organisation:              organization X.520
                                                  -name
Information about the   Originating-
client software of the  Client:
originator.

Phone number of the     Phone:                     O/R         X.420
originator.                                        Descriptor, (X.520)
                                                  telephone-
                                                  number

Used in Usenet News     Supersedes:
in similar ways to
the "Obsoletes" attri-
bute described earlier
in this document.

                         4. Acknowledgments

Harald Tveit Alvestrand and several other people has helped me with
compiling this list. I alone take responsibility for any errors which
may be in the list.



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An earlier version of this list has been published as part of [7].

                           5. References

[1]  J. Postel: "Simple Mail Transfer Protocol", STD 10, RFC 821,
    August 1982.

[2]  D. Crocker: "Standard for the format of ARPA Internet text
    messages." STD 11, RFC 822, August 1982.

[3]  M.R. Horton, R. Adams: "Standard for interchange of USENET
    messages", RFC 1036, December 1987.

[4]  S. Hardcastle-Kille: "Mapping between X.400(1988) / ISO 10021
    and RFC 822",  RFC 1327 May 1992.

[5]  H. Alvestrand & J. Romaguera: "Rules for Downgrading Messages
    from X.400/88 to X.400/84 When MIME Content-Types are Present
    in the Messages", RFC 1496, August 1993.

[6]  1521 N. Borenstein & N. Freed: "MIME (Multipurpose Internet
    Mail Extensions) Part One: Mechanisms for Specifying and
    Describing the Format of Internet Message Bodies",
    RFC 1521, September 1993.

[7]  J. Palme: "Electronic Mail", Artech House publishers, London-
    Boston January 1995.

[8]  H. Alvestrand: "Tags for the Identification of Languages",
    RFC 1766, February 1995.

                         6. Author's address

Jacob Palme                          Phone: +46-8-16 16 67
Stockholm University/KTH             Fax: +46-8-783 08 29
Electrum 230                         E-mail: jpalme@dsv.su.se
S-164 40 Kista, Sweden

                            Appendix A:
Attributes sorted by Internet RFC document in which they appear.

RFC 821
-------

DATA
MAIL FROM
RCPT TO

RFC 822
-------



<mail-attributes-01.txt>   Common Internet Message Attributes   June 1994Palme                                                            [Page 1]


Bcc
Cc
Comments
Date
From
In-Reply-To
Keywords
Message-ID
Received
References
Reply-To
Resent-
Resent-bcc
Resent-Date
Resent-From
Resent-From
Resent-Message-ID
Resent-Reply-To
Resent-ToResent-cc
Return-Path
Sender
Sender
Subject
To

RFC 1036
--------

Approved
Control
Distribution
Expires
Followup-To
Lines
Newsgroups
Organization
Path
Summary

RFC 1327
--------

Alternate-recipient
Auto-Forwarded
Autoforwarded
Content-identifier
Content-Return
Conversion
Conversion-With-Loss
Delivery-Date



<mail-attributes-01.txt>   Common Internet Message Attributes   June 1994Palme                                                            [Page 1]

Discarded-X400-IPMS-Extensions
Discarded-X400-MTS-Extensions
Disclose-Recipients
DL-Expansion-History
Expiry-Date
Generate-Delivery-Report
Importance
Incomplete-Copy
Language
Message-Type Delivery
Obsoletes
Original-Encoded-Information-Types
Prevent-NonDelivery-Report
Priority
Reply-By
Report
Sensitivity

RFC 1521
--------

Content-description
Content-ID
Content-Transfer-Encoding
Content-Type
MIME-Version

Not Internet standard
---------------------

Apparently-to
Content-length
Encoding
Errors-To
Return-Receipt-To
Fax
Telefax
Fcc
Mail-System-Version
Mailer
Organisation
Originating-Client
Phone
Supersedes










<mail-attributes-01.txt>   Common Internet Message Attributes   June 1994