TOC 
Network Working GroupG. Klyne
Internet-DraftNine by Nine
Expires: August 19, 2004J. Palme
 Stockholm University/KTH
 February 19, 2004

Registration of mail and MIME header fields
draft-klyne-hdrreg-mail-02

Status of this Memo

This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026.

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."

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This Internet-Draft will expire on August 19, 2004.

Copyright Notice

Copyright (C) The Internet Society (2004). All Rights Reserved.

Abstract

This document defines the initial IANA registration for permanent mail and MIME message header fields, per [[[RFC XXXX]]] [1].

Discussion of this document

Please send comments to <ietf-822@imc.org>. To subscribe to this list, send a message with the body 'subscribe' to <ietf-822-request@imc.org>.



 TOC 

Table of Contents




 TOC 

1. Introduction

This document defines IANA registration for a number of mail message and MIME header fields, per Registration procedures for message header fields[1].

[[[The main body of this document is automatically generated. Some sample HTML registry pages have been prepared from the same data, and can be found at http://www.ninebynine.org/IETF/Messaging/HdrRegistry/Intro.html.]]]

1.1 Structure of this document

Section Registration templates contains the submission for initial registration of mail related message headers fields.

1.2 Document terminology and conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [10].

NOTE: indented comments like this provide additional nonessential information about the rationale behind this document.

[[[Editorial comments and questions about outstanding issues are provided in triple brackets like this. These working comments should be resolved and removed prior to final publication.]]]



 TOC 

2. Registration templates

Header registry entries are summarized in tabular form for convenience of reference, and presented in full in the following sections.

2.1 Permanent mail header field registrations

Header name         Protocol
-----------         --------
Date                Mail      Message date and time
From                Mail      Mailbox of message author
Sender              Mail      Mailbox of message sender
Reply-To            Mail      Mailbox for replies to message
To                  Mail      Primary recipient mailbox
Cc                  Mail      Carbon-copy recipient mailbox
Bcc                 Mail      Blind-carbon-copy recipient
                              mailbox
Message-ID          Mail      Message identifier
In-Reply-To         Mail      Original message identifier(s)
References          Mail      Related message identifier(s)
Subject             Mail      Topic of message
Comments            Mail      Additional comments about the
                              message
Keywords            Mail      Message key words and/or phrases
Resent-Date         Mail      Date and time message is resent
Resent-From         Mail      Mailbox of person for whom message
                              is resent
Resent-Sender       Mail      Mailbox of person who actually
                              resends the message
Resent-To           Mail      Mailbox to which message is resent
Resent-Cc           Mail      Mailbox(es) to which message is
                              cc'ed on resend
Resent-Bcc          Mail      Mailbox(es) to which message is
                              bcc'ed on resend
Resent-Message-ID   Mail      Message identifier for resent
                              message
Return-Path         Mail      Message return path
Received            Mail      Mail transfer trace information
Disposition-Notification-To
                    Mail      Mailbox for sending disposition
                              notification
Disposition-Notification-Options
                    Mail      Disposition notification options
Original-Recipient  Mail      MDN original recipient information
Originator          Mail      Similar to 'Sender:'
PICS-Label          Mail      PICS rating label
Encoding            Mail      Message encoding and other
                              information
List-Archive        Mail      URL of mailing list archive
List-Help           Mail      URL for mailing list information
List-ID             Mail      Mailing list identifier
List-Owner          Mail      URL for mailing list owner's
                              mailbox
List-Post           Mail      URL for mailing list posting
List-Subscribe      Mail      URL for mailing list subscription
List-Unsubscribe    Mail      URL for mailing list
                              unsubscription
Message-Context     Mail      Type or context of message
DL-Expansion-History
                    Mail      Trace of distribution lists passed
Alternate-Recipient Mail      Controls forwarding to alternate
                              recipients
Original-Encoded-Information-Types
                    Mail      Body part types in message
Content-Return      Mail      Return content on non-delivery?
Generate-Delivery-Report
                    Mail      Request delivery report generation
Prevent-NonDelivery-Report
                    Mail      Non-delivery report required?
Obsoletes           Mail      Reference message to be replaced
Content-Identifier  Mail      Message content identifier
Delivery-Date       Mail      Message delivery time
Expiry-Date         Mail      Message expiry time
Reply-By            Mail      Time by which a reply is requested
Importance          Mail      Message importance
Incomplete-Copy     Mail      Body parts are missing.
Priority            Mail      Message priority
Sensitivity         Mail      Message content sensitivity
Language            Mail      X.400 message content lenguage
Conversion          Mail      Conversion allowed?
Conversion-With-Loss
                    Mail      Lossy conversion allowed?
Message-Type        Mail      Message type: delivery report?
Autoforwarded       Mail      Automatically forwarded indicator
Discarded-X400-IPMS-Extensions
                    Mail      X.400 IPM extensions discarded
Discarded-X400-MTS-Extensions
                    Mail      X.400 MTS extensions discarded
Disclose-Recipients Mail      Disclose names of other
                              recipients?

2.1.1 Header field: Date

Description:
Message date and time
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.1)
Related information:
Specifies the date and time at which the creator of the message indicated that the message was complete and ready to enter the mail delivery system.

2.1.2 Header field: From

Description:
Mailbox of message author
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.2)
Related information:
Specifies the author(s) of the message, that is, the mailbox(es) of the person(s) or system(s) responsible for the writing of the message.

2.1.3 Header field: Sender

Description:
Mailbox of message sender
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.2)
Related information:
Specifies the mailbox of the agent responsible for the actual transmission of the message.

2.1.4 Header field: Reply-To

Description:
Mailbox for replies to message
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.2)
Related information:
When the "Reply-To:" field is present, it indicates the mailbox(es) to which the author of the message suggests that replies be sent.

2.1.5 Header field: To

Description:
Primary recipient mailbox
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.3)
Related information:
Contains the address(es) of the primary recipient(s) of the message.

2.1.6 Header field: Cc

Description:
Carbon-copy recipient mailbox
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.3)
Related information:
Contains the addresses of others who are to receive the message, though the content of the message may not be directed at them.

2.1.7 Header field: Bcc

Description:
Blind-carbon-copy recipient mailbox
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.3)
Related information:
Contains addresses of recipients of the message whose addresses are not to be revealed to other recipients of the message.

2.1.8 Header field: Message-ID

Description:
Message identifier
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.4)
Related information:
Contains a single unique message identifier that refers to a particular version of a particular message. If the message is resent without changes, the original Message-ID is retained.

2.1.9 Header field: In-Reply-To

Description:
Original message identifier(s)
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.4)
Related information:
The message identifier(s) of the original message(s) to which the current message is a reply.

2.1.10 Header field: References

Description:
Related message identifier(s)
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.4)
Related information:
The message identifier(s) of other message(s) to which the current message may be related. In RFC2822, the definition was changed to say that this header field contains a list of all Message-IDs of messages in the preceding reply chain.

2.1.11 Header field: Subject

Description:
Topic of message
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.5)
Related information:
Contains a short string identifying the topic of the message.

2.1.12 Header field: Comments

Description:
Additional comments about the message
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.5)
Related information:
Contains any additional comments on the text of the body of the message. Warning: Some mailers will not show this field to recipients.

2.1.13 Header field: Keywords

Description:
Message key words and/or phrases
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.5)
Related information:
Contains a comma-separated list of important words and phrases that might be useful for the recipient.

2.1.14 Header field: Resent-Date

Description:
Date and time message is resent
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.6)
Related information:
Contains the date and time that a message is reintroduced into the message transfer system.

2.1.15 Header field: Resent-From

Description:
Mailbox of person for whom message is resent
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.6)
Related information:
Contains the mailbox of the agent who has reintroduced the message into the message transfer system, or on whose behanlf the message has been resent.

2.1.16 Header field: Resent-Sender

Description:
Mailbox of person who actually resends the message
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.6)
Related information:
Contains the mailbox of the agent who has reintroduced the message into the message transfer system, if this is different from the Resent-from value.

2.1.17 Header field: Resent-To

Description:
Mailbox to which message is resent
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.6)
Related information:
Contains the mailbox(es) to which the message has been resent.

2.1.18 Header field: Resent-Cc

Description:
Mailbox(es) to which message is cc'ed on resend
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.6)
Related information:
Containes the mailbox(es) to which message is cc'ed on resend

2.1.19 Header field: Resent-Bcc

Description:
Mailbox(es) to which message is bcc'ed on resend
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.6)
Related information:
Containes the mailbox(es) to which message is bcc'ed on resend

2.1.20 Header field: Resent-Message-ID

Description:
Message identifier for resent message
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.6)
Related information:
Contains a message identifier for a resent message

2.1.21 Header field: Return-Path

Description:
Message return path
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.7)
Related information:
Return path for message response diagnostics. See also, RFC 2821.

2.1.22 Header field: Received

Description:
Mail transfer trace information
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2822.txt (section 3.6.7)
Related information:
Contains information about receipt of the current message by a mail transfer agent on the transfer path. See also, RFC 2821.

2.1.23 Header field: Disposition-Notification-To

Description:
Mailbox for sending disposition notification
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2298.txt
Related information:
Indicates that the sender wants a disposition notification when this message is received (read, processed, etc.) by its recipients.

2.1.24 Header field: Disposition-Notification-Options

Description:
Disposition notification options
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2298.txt
Related information:
For optional modifiers on disposition notification requests.

2.1.25 Header field: Original-Recipient

Description:
MDN original recipient information
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2298.txt
Related information:
Original Recipient information for inclusion in disposition notifications.

2.1.26 Header field: Originator

Description:
Similar to 'Sender:'
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
experimental
Author/change controller:
Carl Malamud (mailto:carl@malamud.com)
Internet Multicasting Service.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc1528.txt
Related information:
Sometimes used in Usenet News in similar ways to 'Sender:' Also used in printing protocols. Non-standard in Usenet News, Experimental in RFC 1528 (tcp.int).

2.1.27 Header field: PICS-Label

Description:
PICS rating label
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standard
Author/change controller:
W3C (mailto:web-human@w3.org)
World Wide Web Consortium.
Specification document(s):
http://www.w3.org/TR/REC-PICS-labels
Related information:
Ratings label to control selection (filtering) of messages according to the PICS protocol. Specified for general use with RFC822 message format, with HTTP-specific extensions

2.1.28 Header field: Encoding

Description:
Message encoding and other information
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
experimental
Author/change controller:
Albert K. Costanzo (mailto:AL@AKC.COM)
AKC Consulting Inc..
Specification document(s):
http://www.rfc-editor.org/rfc/rfc1505.txt
Related information:
Used in several different ways by different mail systems. Some use it for a kind of content-type information, some for encoding and length information, some for a kind of boundary information, some in other ways.

2.1.29 Header field: List-Archive

Description:
URL of mailing list archive
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2369.txt
Related information:
Contains URL to use to browse the archives of the mailing list from which this message was relayed.

2.1.30 Header field: List-Help

Description:
URL for mailing list information
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2369.txt
Related information:
Contains URL to use to get a information about the mailing list from which this message was relayed.

2.1.31 Header field: List-ID

Description:
Mailing list identifier
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc1919.txt
Related information:
Stores an identification of the mailing list, through which this message was distributed.

2.1.32 Header field: List-Owner

Description:
URL for mailing list owner's mailbox
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2369.txt
Related information:
Contains URL to send e-mail to the owner of the mailing list from which this message was relayed.

2.1.33 Header field: List-Post

Description:
URL for mailing list posting
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2369.txt
Related information:
Contains URL to use to send contributions to the mailing list from which this message was relayed.

2.1.34 Header field: List-Subscribe

Description:
URL for mailing list subscription
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2369.txt
Related information:
Contains URL to use to get a subscription to the mailing list from which this message was relayed.

2.1.35 Header field: List-Unsubscribe

Description:
URL for mailing list unsubscription
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2369.txt
Related information:
Contains URL to use to unsubscribe the mailing list from which this message was relayed.

2.1.36 Header field: Message-Context

Description:
Type or context of message
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
Standards track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc3458.txt
Related information:
Provides information about the context and presentation characteristics of a message. Can have the values 'voice-message', 'fax-message', 'pager-message', 'multimedia-message', 'text-message', 'none'.

2.1.37 Header field: DL-Expansion-History

Description:
Trace of distribution lists passed
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Trace of distribution lists passed. (MIXER X.400 mapping, not for general use.)

2.1.38 Header field: Alternate-Recipient

Description:
Controls forwarding to alternate recipients
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Controls whether this message may be forwarded to alternate recipients such as a postmaster if delivery is not possible to the intended recipient. Default: Allowed. RFC 2156 (MIXER), not for general usage.

2.1.39 Header field: Original-Encoded-Information-Types

Description:
Body part types in message
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Which body part types occur in this message. RFC 2156 (MIXER), not for general use.

2.1.40 Header field: Content-Return

Description:
Return content on non-delivery?
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Indicates whether the content of a message is to be returned with non-delivery notifications. RFC 2156 (MIXER), not for general use.

2.1.41 Header field: Generate-Delivery-Report

Description:
Request delivery report generation
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Indicates whether a delivery report is wanted at successful delivery. Default is not to generate such a report. RFC 2156 (MIXER), not for general usage.

2.1.42 Header field: Prevent-NonDelivery-Report

Description:
Non-delivery report required?
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Indicates whether non-delivery report is wanted on delivery error. Default is to generate such a report. RFC 2156 (MIXER), not for general usage.

2.1.43 Header field: Obsoletes

Description:
Reference message to be replaced
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Reference to a previous message being corrected and replaced. Compare to 'Supersedes:' used in Usenet News. This field may in the future be replaced with a different name. RFC 2156 (MIXER), not for general usage.

2.1.44 Header field: Content-Identifier

Description:
Message content identifier
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
A text string which identifies the content of a message. RFC 2156 (MIXER), not for general usage.

2.1.45 Header field: Delivery-Date

Description:
Message delivery time
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
The time when a message was delivered to its recipient. RFC 2156 (MIXER), not for general use.

2.1.46 Header field: Expiry-Date

Description:
Message expiry time
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Time at which a message loses its validity. This field may in the future be replaced by 'Expires:'. RFC 2156 (MIXER), not for general use.

2.1.47 Header field: Reply-By

Description:
Time by which a reply is requested
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Latest time at which a reply is requested (not demanded). RFC 2156 (MIXER), not for general usage.

2.1.48 Header field: Importance

Description:
Message importance
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
A hint from the originator to the recipients about how important a message is. Values: High, normal or low. Not used to control transmission speed. Proposed for use with RFC 2156 (MIXER) and RFC 2421 (VPIM).

2.1.49 Header field: Incomplete-Copy

Description:
Body parts are missing.
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Body parts are missing. RFC 2156 (MIXER), not for general usage.

2.1.50 Header field: Priority

Description:
Message priority
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Can be 'normal', 'urgent' or 'non-urgent' and can influence transmission speed and delivery. RFC 2156 (MIXER), not for general use.

2.1.51 Header field: Sensitivity

Description:
Message content sensitivity
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
How sensitive it is to disclose this message to other people than the specified recipients. Values: Personal, private, company confidential. The absence of this header field in messages gatewayed from X.400 indicates that the message is not sensitive. Proposed for use with RFC 2156 (MIXER) and RFC 2421 (VPIM).

2.1.52 Header field: Language

Description:
X.400 message content lenguage
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Can include a code for the natural language used in a message, e.g. 'en' for English. See also 'Content-Language'. RFC 2156 (MIXER), not for general usage.

2.1.53 Header field: Conversion

Description:
Conversion allowed?
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
The body of this message may not be converted from one character set to another. Values: Prohibited and allowed. RFC 2156 (MIXER), not for general use.

2.1.54 Header field: Conversion-With-Loss

Description:
Lossy conversion allowed?
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
The body of this message may not be converted from one character set to another if information will be lost. Values: Prohibited and allowed. RFC 2156 (MIXER), not for general use.

2.1.55 Header field: Message-Type

Description:
Message type: delivery report?
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Only used with the value 'Delivery Report' to indicates that this is a delivery report gatewayed from X.400. RFC 2156 (MIXER), not for general use.

2.1.56 Header field: Autoforwarded

Description:
Automatically forwarded indicator
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Has been automatically forwarded. RFC 2156 (MIXER), not for general usage.

2.1.57 Header field: Discarded-X400-IPMS-Extensions

Description:
X.400 IPM extensions discarded
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Can be used in Internet mail to indicate X.400 IPM extensions which could not be mapped to Internet mail format. RFC 2156 (MIXER), not for general usage.

2.1.58 Header field: Discarded-X400-MTS-Extensions

Description:
X.400 MTS extensions discarded
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Can be used in Internet mail to indicate X.400 MTS extensions which could not be mapped to Internet mail format. RFC 2156 (MIXER), not for general usage.

2.1.59 Header field: Disclose-Recipients

Description:
Disclose names of other recipients?
Applicable protocol:
Mail (http://www.rfc-editor.org/rfc/rfc2822.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2156.txt
Related information:
Tells whether recipients are to be told the names of other recipients of the same message. This is primarily an X.400 facility. In X.400, this is an envelope attribute and refers to disclosure of the envelope recipient list. Disclosure of other recipients is in Internet mail done via the To:, cc: and bcc: header fields. Not for general use.

2.2 Permanent MIME header field registrations

Header name         Protocol
-----------         --------
MIME-Version        MIME      MIME version number
Content-ID          MIME      Identify content body part
Content-Description MIME      Description of message body part
Content-Transfer-Encoding
                    MIME      Content transfer encoding applied
Content-Type        MIME      MIME content type
Content-Base        MIME      Base to be used for resolving
                              relative URIs within this content
                              part.
Content-Location    MIME      URI for retrieving a body part
Content-features    MIME      Indicates content features of a
                              MIME body part
Content-Disposition MIME      Intended content disposition and
                              file name
Content-Language    MIME      Language of message content
Content-Alternative MIME      Alternative content available
Content-MD5         MIME      MD5 checksum of content

2.2.1 Header field: MIME-Version

Description:
MIME version number
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2045.txt (section 4)
Related information:
An indicator that this message is formatted according to the MIME standard, and an indication of which version of MIME is utilized.

2.2.2 Header field: Content-ID

Description:
Identify content body part
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2045.txt (section 7)
Related information:
Specifies a Unique ID for one MIME body part of the content of a message.

2.2.3 Header field: Content-Description

Description:
Description of message body part
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2045.txt (section 8)
Related information:
Description of a particular body part of a message, for example a caption for an image body part.

2.2.4 Header field: Content-Transfer-Encoding

Description:
Content transfer encoding applied
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2045.txt (section 6)
Related information:
Coding method used in a MIME message body part.

2.2.5 Header field: Content-Type

Description:
MIME content type
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2045.txt (section 5)
Related information:
Format of content (character set etc.) Note that the values for this header field are defined in different ways in RFC 1049 and in MIME (RFC 2045), look for the 'MIME-version' header 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. RFC 1049 has 'historic' status. RFC 1766 defines a parameter 'difference' to this header field. Various other Content-Type define various additional parameters. For example, the parameter 'charset' is mandatory for all textual Content-Types. See also: RFC 1049, RFC 1123: 5.2.13, RFC 1766: 4.1.

2.2.6 Header field: Content-Base

Description:
Base to be used for resolving relative URIs within this content part.
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2110.txt
Related information:
Base to be used for resolving relative URIs within this content part.

2.2.7 Header field: Content-Location

Description:
URI for retrieving a body part
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2110.txt
Related information:
URI using which the content of this body-part part was retrieved, might be retrievable, or which otherwise gives a globally unique identification of the content.

2.2.8 Header field: Content-features

Description:
Indicates content features of a MIME body part
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2912.txt (section 3)
Related information:
The 'Content-features:' header can be used to annotate a MIME body part with a media feature expression, to indicate features of the body part content. See also: RFC 2533, RFC 2506, RFC 2045.

2.2.9 Header field: Content-Disposition

Description:
Intended content disposition and file name
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
experimental
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc2183.txt
Related information:
Whether a MIME body part is to be shown inline or is an attachment; can also indicate a suggested filename for use when saving an attachment to a file.

2.2.10 Header field: Content-Language

Description:
Language of message content
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc3282.txt
Related information:
Can include a code for the natural language used in a message, e.g. 'en' for English. Can also contain a list of languages for a message containing more than one language.

2.2.11 Header field: Content-Alternative

Description:
Alternative content available
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
work-in-progress
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc3297.txt
Related information:
Information about the media features of alternative content formats available for the current message.

2.2.12 Header field: Content-MD5

Description:
MD5 checksum of content
Applicable protocol:
MIME (http://www.rfc-editor.org/rfc/rfc2045.txt)
Status:
standards-track
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force.
Specification document(s):
http://www.rfc-editor.org/rfc/rfc1864.txt
Related information:
Checksum of content to ensure that it has not been modified.



 TOC 

3. IANA considerations

This specification provides initial registrations of mail and MIME headers in the "Permanent Message Header Field Registry", defined by Registration procedures for message header fields[1].



 TOC 

4. Security considerations

No security considerations are introduced by this specification beyond those already inherent in the use of message headers.



 TOC 

5. Acknowledgements

Most of the information in this document has been derived from Jacob Palme's work in RFC 2076[8] and subsequent updates [20].

The authors also gratefully acknowledge the contributions of: Mark Nottingham, [[[...]]]



 TOC 

References

[1] Klyne, G., Nottingham, M. and J. Mogul, "Registration procedures for message headers", Oct 2003.
[2] Alvestrand, H., Jordan, K. and 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.
[3] Costanzo, A., Robinson, D. and R. Ullmann, "Encoding Header Field for Internet Messages", RFC 1505, August 1993.
[4] Alvestrand, H., "Tags for the Identification of Languages", RFC 1766, March 1995.
[5] Myers, J. and M. Rose, "The Content-MD5 Header Field", RFC 1864, October 1995.
[6] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996.
[7] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, November 1996.
[8] Palme, J., "Common Internet Message Headers", RFC 2076, February 1997.
[9] Palme, J. and A. Hopmann, "MIME E-mail Encapsulation of Aggregate Documents, such as HTML (MHTML)", RFC 2110, March 1997 (TXT, HTML, XML).
[10] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 (TXT, HTML, XML).
[11] Kille, S., "MIXER (Mime Internet X.400 Enhanced Relay): Mapping between X.400 and RFC 822/MIME", RFC 2156, January 1998.
[12] Troost, R., Dorner, S. and K. Moore, "Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field", RFC 2183, August 1997 (TXT, HTML, XML).
[13] Fajman, R., "An Extensible Message Format for Message Disposition Notifications", RFC 2298, March 1998 (TXT, HTML, XML).
[14] Neufeld, G. and J. Baer, "The Use of URLs as Meta-Syntax for Core Mail List Commands and their Transport through Message Header Fields", RFC 2369, July 1998 (TXT, HTML, XML).
[15] Vaudreuil, G. and G. Parsons, "Voice Profile for Internet Mail - version 2", RFC 2421, September 1998 (TXT, HTML, XML).
[16] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, April 2001.
[17] Resnick, P., "Internet Message Format", RFC 2822, April 2001.
[18] Klyne, G., "Indicating Media Features for MIME Content", RFC 2912, September 2000.
[19] Chandhok, R. and G. Wenger, "List-Id: A Structured Field and Namespace for the Identification of Mailing Lists", RFC 2919, March 2001.
[20] Palme, J., "Common Internet Message Header Fields", Internet draft draft-palme-mailext-headers-06, November 2001.


 TOC 

Authors' Addresses

  Graham Klyne
  Nine by Nine
  UK
EMail:  GK-IETF@ninebynine.org
URI:  http://www.ninebynine.net/
  
  Jacob Palme
  Stockholm University/KTH
  Forum 100
  Kista S-164 40
  Sweden
Phone:  +46-8-16 16 67
EMail:  jpalme@dsv.su.se


 TOC 

Appendix A. Revision history

[[[Please remove this section on final publication]]]

A.1 draft-klyne-hdrreg-mail-02

02d 19-Feb-2004:
  • Incorporated small changes to specific header field descriptions, suggested by Jacob.

02c 18-Feb-2004:
  • Separated Mail and MIME header fields.
  • Corrected specification reference for MIXER headers (RFC 2156).
  • Changed applicable protocol for MIME header fields.
  • Other smaller corrections.

02b 17-Feb-2004:
  • Removed provisional mail header registrations from this document.

02a 05-Aug-2002:
  • Added Jacob Palme as co-editor.

A.2 draft-klyne-hdrreg-mail-01

01c 05-Jun-2002:
  • Minor editorial.

01b 10-May-2002:
  • Updated some contact information.
  • Regenerated registry tables with revised software.

01a 08-May-2002:
  • Revised change controller information in line with registry specification.
  • Cleaned up some table layout.

A.3 draft-klyne-hdrreg-mail-00

00c 05-May-2002:
  • Added data for permanent and provisional registries.

00b 01-May-2002:
  • Revised form of registry entry content. (Auto-generated from RDF data.)

00a 22-Jan-2002:
  • Document initially created.



 TOC 

Appendix B. TODO:

[[[Please remove this section on final publication]]]



 TOC 

Intellectual Property Statement

Full Copyright Statement

Acknowledgement