One document matched: draft-ietf-mailext-mail-attributes-02.txt
Differences from draft-ietf-mailext-mail-attributes-01.txt
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 1123, RFC 1327, RFC 1496, RFC 1521 and RFC 1766. 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, in which the attribute is defined.
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Table of contents
1. Introduction
2. Use of gatewaying attributes
3. Table of attributes
3.1 Phrases used in the tables
3.2 Addressing information
3.3 Envelope and format information
3.4 Sender and recipient indication
3.5 Response control
3.6 Message identification and referral attributes
3.7 Other textual attributes
3.8 Attributes containing dates and times
3.9 Quality information
3.10 Language information
3.11 Size information
3.13 Encoding information
3.14 Resent-attributes
3.15 Miscellaneous
4. Acknowledgments
5. References
6. Author's address
Appendix A: Attributes sorted by Internet RFC document in which
they appear
Appendix B: Alphabetical index
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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 1123 [5], RFC 1327 [7], RFC 1496 [8], RFC 1521 [11]
and RFC 1766 [12]. 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 but are not part of any Internet standard 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.
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 has but which were
previously not standardized in Internet mail. The fact that an
attribute occurs in RFC 1327 indicates that it is recommended for
use in gatewaying messages between X.400 and Internet mail, but
does not mean that the attribute is recommended for messages wholly
within Internet mail. Some of these attributes may eventually get
accepted also for usage within Internet mail, but they are, when
this is written (July 1995) not recommended for such usage.
Fields defined in RFC 1036 for use in Usenet News sometimes appear
in mail messages, either because the messages have been gatewayed
from Usenet News to e-mail, or because the messages were written in
combined clients supporting both e-mail and Usenet News in the same
client. These fields are however not standardized for use in
Internet e-mail and should be handled with caution.
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.
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3. Table of attributes
3.1 Phrases used in the tables
"not for general Used to mark attributes which are defined in
usage" RFC 1327 for use in messages from or to
Internet mail/X.400 gateways. These attributes
have not been standardized for general usage
in the exchange of messages between Internet
mail-based systems.
"not standardized Used to mark attributes defined only in RFC
for use in e-mail" 1036 for use in Usenet News. These attributes
have no standard meaning when appearing in e-
mail, some of them may even be used in
different ways by different software. When
appearing in e-mail, they should be handled
with caution. Note that RFC 1036, although
generally used as a standard for Usenet News,
is not an accepted IETF standard or on the
IETF standards track.
"non-standard" This attribute is not specified in any of
those referenced RFC-s which are Internet
standards, draft standards or proposed
standards. The attribute appears here because
it is common in e-mail or Usenet News headers.
Usage of these attributes is not in general
recommended.
"discouraged" This attribute, which is non-standard, is
known to create problems and should not be
generated. Handling of such attributes in
incoming mail should be done with great
caution.
"controversial" The meaning and usage of this attribute is
controversial, i.e. different implementors
have chosen to implement the attribute in
different ways. Because of this, such
attributes should be handled with caution and
understanding of the different possible
interpretations.
"for limited use" A so-called "experimental" Internet standard.
These should be used only if both parties
agree.
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3.2 Addressing information
Original sender. Should in MAIL FROM RFC 821,
Internet be empty ("MAIL FROM: RFC 1123: 5.2.9.
<>") when sending notifications,
and be the list administrator
when forwarding from a
distribution list. This value may
for gatewayed messages contain a
chain of hosts to be passed in
sequence to reach the original
sender (i.e. a relative address).
Used to convey the information Return-Path: RFC 821,
from the MAIL FROM envelope RFC 1123: 5.2.13.
attribute when the message leaves
the SMTP environment in which
"MAIL FROM" is used.
Recipient to which message is to RCPT TO RFC 821,
be delivered. Relative address RFC 1123: 5.2.6.
was allowed in RFC 821, but later
prohibited in RFC 1123.
3.3 Envelope and format
information
All that is inside the envelope. DATA RFC 821,
RFC 1123: 5.2.8.
Trace of MTA-s which a message Received: RFC 822: 4.3.2,
has passed. RFC 1123: 5.2.8.
An indicator that this message is MIME-Version: RFC 1521: 3.
formatted according to the MIME
standard, and an indication of
which version of MIME is
utilized.
List of MTA-s passed. Path: RFC 1036: 2.2.6,
not standardized
for use in e-mail.
Special Usenet News actions. Control: RFC 1036: 2.1.6,
not standardized
for use in
e-mail.
Trace of distribution lists DL-Expansion- RFC 1327, not for
passed. History- general usage.
Indication
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Which body part types occur in Original- RFC 1327, not for
this message. Encoded- general usage.
Information-
Types:
Special informational message. Message-Type: RFC 1327, not for
Delivery general usage.
Report
Controls whether this message may Alternate- RFC 1327, not for
be forwarded to alternate Recipient: general usage.
recipients such as a postmaster
if delivery is not possible to
the intended recipient. Default:
Allowed.
Whether recipients are to be told Disclose- RFC 1327, not for
the names of other recipients of Recipients: general usage.
the same message. This is
primarily an X.400 facility, such
disclosure is in Internet mail
done via the To:, Cc: and Bcc:
heading fields.
3.4 Sender and recipient
indication
Author, approver From: RFC 822: 4.4.1,
RFC 1123: 5.2.15-
16, 5.3.7.
Moderator Approved: RFC 1036: 2.2.11,
not standardized
for use in e-mail.
Sender information inside the Sender: RFC 822: 4.4.2,
envelope. RFC 1123: 5.2.15-
16, 5.3.7.
Main recipients. To: RFC 822: 4.5.1,
RFC 1123: 5.2.15-
16, 5.3.7.
Additional recipients. Cc: RFC 822: 4.5.2,
RFC 1123. 5.2.15-
16, 5.3.7.
Recipients not shown to other Bcc: RFC 822: 4.5.3,
recipients. RFC 1123: 5.2.15-
16, 5.3.7.
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In Usenet News: group to which Newsgroups: RFC 1036: 2.1.3,
this article was posted. not standardized
Some systems provide this field and controversial
also in e-mail although it is not for use in e-mail.
standardized there.
Unfortunately, the field can
appear in e-mail with two
different and contradictory
meanings:
(a) Indicates the newsgroup
recipient of a message sent to
both e-mail and Usenet News
recipients.
(b) In a personally addressed
reply to a message in a
newsgroup, indicates the
newsgroup in which this
discussion originated.
Inserted by Sendmail when there Apparently- Non-standard,
is no "To:" recipient in the To: discouraged,
original message, listing mentioned in
recipients derived from the RFC 1211.
envelope into the message
heading. This behavior is not
quite proper, MTA-s should not
modify headings (except inserting
Received lines), and it can in
some cases cause Bcc recipients
to be wrongly divulged to non-Bcc
recipients.
Limitation on where this message Distribution: RFC 1036: 2.2.7,
can be distributed. not standardized
for use in e-mail.
Fax number of the originator. Fax:, Non-standard.
Telefax:
Phone number of the originator. Phone: Non-standard.
Information about the client Mail-System- Non-standard.
software of the originator. Version:,
Mailer:,
Originating-
Client:
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3.5 Response control
Replacement for "From:" to which Reply-To: RFC 822: 4.4.3,
replies are to be sent. controversial.
Unfortunately, the specification
in RFC 822 is ambiguous, since
some people want this to be a
replacement for all recipients in
commands to send replies to all
recipients of the replied-to
message. The most general
consensus, however, seems to be
that "Reply-To" only indicates
replacement for the "From" field,
not for all the recipients.
Where group replies to this Followup-To: RFC 1036: 2.2.3,
message are to be sent. not standardized
for use in e-mail.
Address to which notifications Errors-To:, Non-standard,
are to be sent and a request to Return- discouraged.
get delivery notifications. Receipt-To:
Internet standards recommend,
however, the use of RCPT TO and
Return-Path, not Errors-To, for
where notifications are to be
sent, and a new standard under
development specifies how
requests for notifications are
specified by a new parameter
"NOTIFY" to the "RCPT TO" SMTP
command.
Whether non-delivery report is Prevent- RFC 1327, not for
wanted at delivery error. Default NonDelivery- general usage.
is to want such a report. Report:
Whether a delivery report is Generate- RFC 1327, not for
wanted at successful delivery. Delivery- general usage.
Default is not to generate such a Report:
report.
Indicates whether the content of Content- RFC 1327, not for
a message is to be returned with Return general usage.
non-delivery notifications.
Indicates whether the content of RET in DRPT In forthcoming new
a message is to be returned with SMTP exten- Internet standard.
non-delivery notifications. sion
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3.6 Message identification and
referral attributes
Unique ID of this message. Message-ID: RFC 822: 4.6.1.
Unique ID of one body part of the Content-ID: RFC 1521: 6.1.
content of a message.
Reference to message which this In-Reply-To: RFC 822: 4.6.2.
message is a reply to.
Reference to other related References: RFC 822: 4.6.3.
messages.
Reference to previous message Obsoletes: RFC 1327, not for
being corrected and replaced. general usage.
Used in Usenet News in similar Supersedes: Non-standard.
ways to the "Obsoletes" attribute
described earlier in this
document.
3.7 Other textual attributes
Search keys for data base Keywords: RFC 822: 4.7.1.
retrieval.
Title, heading, subject. Subject: RFC 822: 4.7.1.
Comments on a message. Comments: RFC 822: 4.7.2.
Description of a particular body Content- RFC 1521: 6.2.
part of a message. description:
Organization to which the sender Organization: RFC 1036: 2.2.8,
of this message belongs. not standardized
for use in e-mail.
See Organization. Organisation: Non-standard.
Short text describing a longer Summary: RFC 1036: 2.2.10,
message. not standardized
for use in e-mail.
A text string which identifies Content- RFC 1327, not for
the content of a message. identifier: general usage.
3.8 Attributes containing dates
and times
The time when a message was Delivery- RFC 1327, not for
delivered to its recipient. Date: general usage.
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In Internet, the date when a Date: RFC 822: 5.1,
message was written, in X.400, RFC 1123: 5.2.14.
the time a message was submitted.
A suggested expiration date. Can Expires: RFC 1036: 2.2.4,
be used both to limit the time of not standardized
an article which is not for use in e-mail.
meaningful after a certain date,
and to extend the storage of
important articles.
Time at which a message loses its Expiry-Date: RFC 1327, not for
validity. general usage.
Latest time at which a reply is Reply-By: RFC 1327, not for
requested (not demanded). general usage.
3.9 Quality information
Can be "normal", "urgent" or "non- Priority: RFC 1327, not for
urgent" and can influence general usage.
transmission speed and delivery.
Sometimes used as a priority Precedence: Non-standard,
value which can influence controversial,
transmission speed and delivery. discouraged.
Common values are "bulk" and
"first-class". Other uses is to
control automatic replies and to
control return-of-content
facilities, and to stop mailing
list loops.
Can be high, normal or low and is Importance: RFC 1327, not for
only used in the recipient client general usage.
(UA).
Can be personal, private, company Sensitivity: RFC 1327, not for
confidential or absent. general usage.
Body parts are missing. Incomplete- RFC 1327, not for
Copy: general usage.
3.10 Language information
Can include a code for the Language: RFC 1327, not for
natural language used in a general usage.
message, e.g. "en" for English.
Can include a code for the Content- RFC 1766, proposed
natural language used in a Language: standard.
message, e.g. "en" for English.
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3.11 Size information
Inserted by certain mailers to Content- Non-standard,
indicate the size in bytes of the length: discouraged.
message text. Can cause several
robustness and interoperability
problems and is not recommended.
Size of the message. Lines: RFC 1036: 2.2.12,
not standardized
for use in e-mail.
3.12 Conversion control
The body of this message may not Conversion: RFC 1327, not for
be converted from one character general usage.
set to another.
The body of this message may not Conversion- RFC 1327, not for
be converted from one character With-Loss: general usage.
set to another if information
will be lost.
3.13 Encoding information
Format of content (character set Content-Type: RFC 1049,
etc.) Note that the values for RFC 1123: 5.2.13,
this field is defined in RFC 1521: 4.
different ways in RFC 1049 and in
MIME (RFC 1521), look for the
"MIME-version" heading field to
understand if Content-Type is to
be interpreted according to RFC
1049 or according to MIME. The
MIME definition should be used in
generating mail.
Coding method used in content. Content- RFC 1521: 5.
Transfer-
Encoding
Coding method used in content. Encoding: RFC 1154,
RFC 1505,
for limited use.
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3.14 Resent-attributes
When manually forwarding a Resent-Reply- RFC 822: C.3.3.
message, attributes referring to To:,
the forwarding, not to the Resent-From:,
original message. Note: MIME Resent-
specifies another way of Sender:,
resending messages, using the Resent-From:,
"Message" Content-Type. Resent-Date:,
Resent-To:,
Resent-cc:,
Resent-bcc:,
Resent-
Message-ID:
3.15 Miscellaneous
Name of file in which a copy of Fcc: Non-standard.
this message is stored.
Has been automatically forwarded. Auto- RFC 1327, not for
Forwarded: general usage.
Can be used in Internet mail to Discarded- RFC 1327, not for
indicate X.400 extensions which X400-IPMS- general usage.
could not be mapped to Internet Extensions:
mail format.
Can be used in Internet mail to Discarded- RFC 1327, not for
indicate X.400 extensions which X400-MTS- general usage.
could not be mapped to Internet Extensions:
mail format.
4. Acknowledgments
Harald Tveit Alvestrand, Keith Moore, Nick Smith and several other
people have helped me with compiling this list. I alone take
responsibility for any errors which may still be in the list.
An earlier version of this list has been published as part of [13].
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5. References
Ref. Author, title IETF status
(July 1995)
------ ---------------------------------------------- -----------
[1] J. Postel: "Simple Mail Transfer Protocol", Standard,
STD 10, RFC 821, August 1982. Recommended.
[2] D. Crocker: "Standard for the format of ARPA Standard,
Internet text messages." STD 11, RFC 822, Recommended.
August 1982.
[3] M.R. Horton, R. Adams: "Standard for Non-standard
interchange of USENET messages", RFC 1036, (but still
December 1987. widely used).
[4] M. Sirbu: "A Content-Type header field for Standard,
internet messages", RFC 1049, March 1988. Recommended.
[5] R. Braden (editor): "Requirements for Internet Standard,
Hosts -- Application and Support", STD-3, RFC Required
1123, October 1989.
[6] D. Robinson, R. Ullman: "Encoding Header Field Non-standard.
for Internet Messages", RFC 1154, April 1990.
[7] S. Hardcastle-Kille: "Mapping between Proposed
X.400(1988) / ISO 10021 and RFC 822", RFC standard,
1327 May 1992. elective.
[8] H. Alvestrand & J. Romaguera: "Rules for Proposed
Downgrading Messages from X.400/88 to X.400/84 standard,
When MIME Content-Types are Present in the elective.
Messages", RFC 1496, August 1993.
[9] A. Costanzo: "Encoding Header Field for Non-standard.
Internet Messages", RFC 1154, April 1990.
[10] A. Costanzo, D. Robinson: "Encoding Header Experimental.
Field for Internet Messages", RFC 1505, August
1993.
[11] N. Borenstein & N. Freed: "MIME (Multipurpose Draft
Internet Mail Extensions) Part One: Mechanisms Standard,
for Specifying and Describing the Format of elective.
Internet Message Bodies", RFC 1521, Sept 1993.
[12] H. Alvestrand: "Tags for the Identification of Proposed
Languages", RFC 1766, February 1995. standard,
elective.
[13] J. Palme: "Electronic Mail", Artech House Non-standard.
publishers, London-Boston January 1995.
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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
-------
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
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RFC 1036
--------
Approved
Control
Distribution
Expires
Followup-To
Lines
Newsgroups
Organization
Path
Summary
RFC 1049
--------
Content-Type
RFC 1327
--------
Alternate-recipient
Auto-Forwarded
Autoforwarded
Content-identifier
Content-Return
Conversion
Conversion-With-Loss
Delivery-Date
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 1505
--------
Encoding
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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
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Appendix B:
Alphabetical index
Section Heading-field
------- -------------
3.3 Alternate-Recipient
3.4 Apparently-To
3.4 Approved
3.16 Auto-Forwarded
3.4 Bcc
3.4 Cc
3.7 Comments
3.7 Content-Description
3.6 Content-ID
3.7 Content-identifier
3.10 Content-Language
3.11 Content-Lenght
3.5 Content-Return
3.13 Content-Transfer-Encoding
3.13 Content-Type
3.3 Control
3.12 Conversion
3.12 Conversion-With-Loss
3.3 DATA
3.8 Date
3.8 Delivery-Date
3.16 Discarded-X400-IPMS-Extensions
3.16 Discarded-X400-MTS-Extensions
3.3 Disclose-Recipients
3.4 Distribution
3.3 DL-Expansion-History-Indication
3.13 Encoding
3.5 Errors-To
3.8 Expires
3.4 Fax
3.15 Fcc
3.5 Followup-To
3.4 From
3.5 Generate-Delivery-Report
3.9 Importance
3.6 In-Reply-To
3.9 Incomplete-Copy
3.7 Keywords
3.10 Language
3.11 Lines
3.2 MAIL FROM
3.4 Mail-System-Version
3.4 Mailer
3.6 Message-ID
3.3 Message-Type
3.3 MIME-Version
3.4 Newsgroups
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3.6 Obsoletes
3.7 Organisation
3.7 Organization
3.3 Original-encoded-Information-Types
3.4 Originating-Client
3.3 Path
3.4 Phone
3.9 Precedence
3.5 Prevent-NonDelivery-Report
3.9 Priority
3.2 RCPT TO
3.3 Received
3.6 References
3.8 Reply-By
3.5 Reply-To
3.14 Resent-
3.5 RET in DRPT SMTP extension
3.2 Return-Path
3.5 Return-Receipt-To
3.4 Sender
3.9 Sensitivity
3.7 Subject
3.7 Summary
3.6 Supersedes
3.4 Telefax
3.4 To
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