The Archived-At Message Header Field
RFC 5064

Network Working Group                                          M. Duerst
Request for Comments: 5064                      Aoyama Gakuin University
Category: Standards Track                                  December 2007

                  The Archived-At Message Header Field

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.

Abstract

   This memo defines a new email header field, Archived-At:, to provide
   a direct link to the archived form of an individual email message.

Table of Contents

   1. Introduction ....................................................2
   2. Header Field Definition .........................................2
      2.1. Syntax .....................................................2
      2.2. Multiple Archived-At Header Fields .........................3
      2.3. Interaction with Message Fragmentation and Reassembly ......3
      2.4. Syntax Extension for Internationalized Message Headers .....3
      2.5. The X-Archived-At Header Field .............................4
   3. Implementation and Usage Considerations .........................4
      3.1. Formats of Archived Message ................................4
      3.2. Implementation Considerations ..............................4
      3.3. Usage Considerations .......................................5
   4. Security Considerations .........................................6
   5. IANA Considerations .............................................7
      5.1. Registration of the Archive-At Header Field ................7
      5.2. Registration of the X-Archived-At Header Field .............7
   6. Acknowledgments .................................................8
   7. References ......................................................8
      7.1. Normative References .......................................8
      7.2. Informative References .....................................8

Duerst                      Standards Track                     [Page 1]
RFC 5064          The Archived-At Message Header Field     December 2007

1.  Introduction

   [RFC2369] defines a number of header fields that can be added to
   Internet messages such as those sent by email distribution lists or
   in netnews [RFC1036].  One of them is the List-Archive header field
   that describes how to access archives for the list.  This allows
   access to the archives as a whole, but not an individual message.

   There is often a need or desire to refer to the archived form of a
   single message.  For more detailed usage scenarios, please see
   Section 3.3.  This memo defines a new header, Archived-At, to refer
   to a single message at an archived location.  This provides quick
   access to the location of a mailing list message in the list archive.
   It can also be used independently of mailing lists, for example in
   connection with legal requirements to archive certain messages.

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in [RFC2119].

2.  Header Field Definition

2.1.  Syntax

   For the Archived-At header field, the field name is "Archived-At".
   The field body consist of a URI [STD66] enclosed in angle brackets
   ('<', '>').  The URI MAY contain folding whitespace (FWS, [RFC2822]),
   which is ignored.  Mail Transfer Agents (MTAs) MUST NOT insert
   whitespace within the angle brackets, but client applications SHOULD
   ignore any whitespace, which might have been inserted by poorly
   behaved MTAs.  The URI points to an archived version of the message.
   See Section 3.1 for more details.

   This header field is subject to the encoding and character
   restrictions for mail headers as described in [RFC2822].

   More formally, the header field is defined as follows in Augmented
   BNF (ABNF) according to [RFC4234]:

      archived-at = "Archived-At:" [FWS] "<" folded-URI ">" CRLF
      folded-URI  = <URI, but free insertion of FWS permitted>

   where URI is defined in [STD66], and CRLF and FWS are defined in
   [RFC2822].

   To convert a folded-URI to a URI, first apply standard [RFC2822]
   unfolding rules (replacing FWS with a single SP), and then delete any
   remaining un-encoded SP characters.