Request for Comments: 4021 University of Oxford
Category: Standards Track J. Palme
Stockholm University/KT
March 2005
Registration of Mail and MIME Header Fields
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document defines the initial IANA registration for permanent
mail and MIME message header fields, per RFC 3864.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Structure of This Document . . . . . . . . . . . . . . . 3
1.2. Document Terminology and Conventions . . . . . . . . . . 4
2. Registration Templates . . . . . . . . . . . . . . . . . . . . 4
2.1. Permanent Mail Header Field Registrations . . . . . . . 4
2.1.1. Header Field: Date . . . . . . . . . . . . . . . 6
2.1.2. Header Field: From . . . . . . . . . . . . . . . 7
2.1.3. Header Field: Sender . . . . . . . . . . . . . . 7
2.1.4. Header Field: Reply-To . . . . . . . . . . . . . 8
2.1.5. Header Field: To . . . . . . . . . . . . . . . . 8
2.1.6. Header Field: Cc . . . . . . . . . . . . . . . . 9
2.1.7. Header Field: Bcc . . . . . . . . . . . . . . . 9
2.1.8. Header Field: Message-ID . . . . . . . . . . . . 10
2.1.9. Header Field: In-Reply-To . . . . . . . . . . . 10
2.1.10. Header Field: References . . . . . . . . . . . . 11
2.1.11. Header Field: Subject . . . . . . . . . . . . . 11
2.1.12. Header Field: Comments . . . . . . . . . . . . . 12
2.1.13. Header Field: Keywords . . . . . . . . . . . . . 12
2.1.14. Header Field: Resent-Date . . . . . . . . . . . 13
2.1.15. Header Field: Resent-From . . . . . . . . . . . 13
2.1.16. Header Field: Resent-Sender . . . . . . . . . . 14
2.1.17. Header Field: Resent-To . . . . . . . . . . . . 14
2.1.18. Header Field: Resent-Cc . . . . . . . . . . . . 15
2.1.19. Header Field: Resent-Bcc . . . . . . . . . . . . 15
2.1.20. Header Field: Resent-Reply-To . . . . . . . . . 16
2.1.21. Header Field: Resent-Message-ID . . . . . . . . 16
2.1.22. Header Field: Return-Path . . . . . . . . . . . 17
2.1.23. Header Field: Received . . . . . . . . . . . . . 17
2.1.24. Header Field: Encrypted . . . . . . . . . . . . 18
2.1.25. Header Field: Disposition-Notification-To . . . 18
2.1.26. Header Field: Disposition-Notification-Options . 19
2.1.27. Header Field: Accept-Language . . . . . . . . . 19
2.1.28. Header Field: Original-Message-ID . . . . . . . 20
2.1.29. Header Field: PICS-Label . . . . . . . . . . . . 20
2.1.30. Header Field: Encoding . . . . . . . . . . . . . 21
2.1.31. Header Field: List-Archive . . . . . . . . . . . 21
2.1.32. Header Field: List-Help . . . . . . . . . . . . 22
2.1.33. Header Field: List-ID . . . . . . . . . . . . . 22
2.1.34. Header Field: List-Owner . . . . . . . . . . . . 23
2.1.35. Header Field: List-Post . . . . . . . . . . . . 23
2.1.36. Header Field: List-Subscribe . . . . . . . . . . 24
2.1.37. Header Field: List-Unsubscribe . . . . . . . . . 24
2.1.38. Header Field: Message-Context . . . . . . . . . 25
2.1.39. Header Field: DL-Expansion-History . . . . . . . 25
2.1.40. Header Field: Alternate-Recipient . . . . . . . 26
2.1.41. Header Field: Original-Encoded-Information-Types 26
2.1.42. Header Field: Content-Return . . . . . . . . . . 27
2.1.43. Header Field: Generate-Delivery-Report . . . . . 27
2.1.44. Header Field: Prevent-NonDelivery-Report . . . . 28
2.1.45. Header Field: Obsoletes . . . . . . . . . . . . 28
2.1.46. Header Field: Supersedes . . . . . . . . . . . . 29
2.1.47. Header Field: Content-Identifier . . . . . . . . 29
2.1.48. Header Field: Delivery-Date . . . . . . . . . . 30
2.1.49. Header Field: Expiry-Date . . . . . . . . . . . 30
2.1.50. Header Field: Expires . . . . . . . . . . . . . 31
2.1.51. Header Field: Reply-By . . . . . . . . . . . . . 31
2.1.52. Header Field: Importance . . . . . . . . . . . . 32
2.1.53. Header Field: Incomplete-Copy . . . . . . . . . 32
2.1.54. Header Field: Priority . . . . . . . . . . . . . 33
2.1.55. Header Field: Sensitivity . . . . . . . . . . . 33
2.1.56. Header Field: Language . . . . . . . . . . . . . 34
2.1.57. Header Field: Conversion . . . . . . . . . . . . 34
2.1.58. Header Field: Conversion-With-Loss . . . . . . . 35
2.1.59. Header Field: Message-Type . . . . . . . . . . . 35
2.1.60. Header Field: Autosubmitted . . . . . . . . . . 36
2.1.61. Header Field: Autoforwarded . . . . . . . . . . 36
2.1.62. Header Field: Discarded-X400-IPMS-Extensions . . 37
2.1.63. Header Field: Discarded-X400-MTS-Extensions . . 37
2.1.64. Header Field: Disclose-Recipients . . . . . . . 38
2.1.65. Header Field: Deferred-Delivery . . . . . . . . 38
2.1.66. Header Field: Latest-Delivery-Time . . . . . . . 39
2.1.67. Header Field: Originator-Return-Address . . . . 39
2.1.68. Header Field: X400-Content-Identifier . . . . . 40
2.1.69. Header Field: X400-Content-Return . . . . . . . 40
2.1.70. Header Field: X400-Content-Type . . . . . . . . 41
2.1.71. Header Field: X400-MTS-Identifier . . . . . . . 41
2.1.72. Header Field: X400-Originator . . . . . . . . . 42
2.1.73. Header Field: X400-Received . . . . . . . . . . 42
2.1.74. Header Field: X400-Recipients . . . . . . . . . 43
2.1.75. Header Field: X400-Trace . . . . . . . . . . . . 43
2.2. Permanent MIME Header Field Registrations . . . . . . . 44
2.2.1. Header Field: MIME-Version . . . . . . . . . . . 44
2.2.2. Header Field: Content-ID . . . . . . . . . . . . 45
2.2.3. Header Field: Content-Description . . . . . . . 45
2.2.4. Header Field: Content-Transfer-Encoding . . . . 46
2.2.5. Header Field: Content-Type . . . . . . . . . . . 46
2.2.6. Header Field: Content-Base . . . . . . . . . . . 47
2.2.7. Header Field: Content-Location . . . . . . . . . 47
2.2.8. Header Field: Content-features . . . . . . . . . 48
2.2.9. Header Field: Content-Disposition . . . . . . . 48
2.2.10. Header Field: Content-Language . . . . . . . . . 49
2.2.11. Header Field: Content-Alternative . . . . . . . 49
2.2.12. Header Field: Content-MD5 . . . . . . . . . . . 50
2.2.13. Header Field: Content-Duration . . . . . . . . . 50
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50
4. Security Considerations . . . . . . . . . . . . . . . . . . . 51
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 51
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 51
6.1. Normative References . . . . . . . . . . . . . . . . . . 51
6.2. Informative References . . . . . . . . . . . . . . . . . 53
Authors’ Addresses . . . . . . . . . . . . . . . . . . . . . . . . 53
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 54
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 from RDF/N3
data. Some experimental HTML registry pages have been prepared from
the same data and can be found at [27].
1.1. Structure of This Document
Section 2.1 contains the templates for initial registration of mail
message header fields.
Section 2.2 contains templates for initial registration of MIME
header 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 BCP 14, RFC 2119 [9].
2. Registration Templates
Header field 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 Identify replied-to message(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-Reply-To Mail Resent reply-to
Resent-Message-ID Mail Message identifier for resent
message
Return-Path Mail Message return path
Received Mail Mail transfer trace information
Encrypted Mail Message encryption information
Disposition-Notification-To
Mail Mailbox for sending disposition
notification
Disposition-Notification-Options
Mail Disposition notification options
Accept-Language Mail Language(s) for auto-responses
Original-Message-ID Mail Original message identifier
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
Supersedes Mail Reference message to be replaced
Content-Identifier Mail Message content identifier
Delivery-Date Mail Message delivery time
Expiry-Date Mail Message expiry time
Expires 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 language
Conversion Mail Conversion allowed?
Conversion-With-Loss
Mail Lossy conversion allowed?
Message-Type Mail Message type: delivery report?
Autosubmitted Mail Automatically submitted indicator
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?
Deferred-Delivery Mail Deferred delivery information
Latest-Delivery-Time
Mail Latest delivery time requested
Originator-Return-Address
Mail Originator return address
X400-Content-Identifier
Mail Message content identifier
X400-Content-Return Mail Return content on non-delivery?
X400-Content-Type Mail X400 content type
X400-MTS-Identifier Mail X400 MTS-Identifier
X400-Originator Mail X400 Originator
X400-Received Mail X400 Received
X400-Recipients Mail X400 Recipients
X400-Trace Mail X400 Trace
2.1.1. Header Field: Date
Description:
Message date and time
Applicable protocol: Mail [18]
Status: standard
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force
Specification document(s):
RFC 2822 [18] (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. Defined as standard by RFC 822.
2.1.2. Header Field: From
Description:
Mailbox of message author
Applicable protocol: Mail [18]
Status: standard
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force
Specification document(s):
RFC 2822 [18] (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. Defined as standard by RFC 822.
2.1.3. Header Field: Sender
Description:
Mailbox of message sender
Applicable protocol: Mail [18]
Status: standard
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force
Specification document(s):
RFC 2822 [18] (section 3.6.2)
Related information:
Specifies the mailbox of the agent responsible for the actual
transmission of the message. Defined as standard by RFC 822.
2.1.4. Header Field: Reply-To
Description:
Mailbox for replies to message
Applicable protocol: Mail [18]
Status: standard
Author/change controller:
IETF (mailto:iesg@ietf.org) Internet Engineering Task Force
Specification document(s):
RFC 2822 [18] (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. Defined as standard by RFC 822.
2.1.5. Header Field: To
Description:
Primary recipient mailbox
Applicable protocol: Mail [18]
Status: standard
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force
Specification document(s):
RFC 2822 [18] (section 3.6.3)
Related information:
Contains the address(es) of the primary recipient(s) of the
message. Defined as standard by RFC 822.
2.1.6. Header Field: Cc
Description:
Carbon-copy recipient mailbox
Applicable protocol: Mail [18]
Status: standard
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force
Specification document(s):
RFC 2822 [18] (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.
Defined as standard by RFC 822.
2.1.7. Header Field: Bcc
Description:
Blind-carbon-copy recipient mailbox
Applicable protocol: Mail [18]
Status: standard
Author/change controller:
IETF (mailto:iesg@ietf.org)
Internet Engineering Task Force
Specification document(s):
RFC 2822 [18] (section 3.6.3)
Related information: