Network Working Group Jacob Palme Internet Draft Stockholm University/KTH Sweden Category: Proposed standard February 1995 Expires September 1995 Additional RFC 822 heading attributes 1. 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. 2. Abstract This memo introduces three new e-mail (RFC 822) heading fields, obsoletes, auto-submitted and expires. 3. Introduction This memo introduces certain heading attributes for Internet e-mail (RFC 822) headers which will enhance the e-mail service in various ways. The heading attributes introduced are: Obsoletes, Auto-Submitted and Expires. 4. Relation to X.400 gatewaying recommendation Some of the attributes defined in this document are also defined in recommendations for gatewaying [2] between X.400 [3] and Internet mail. However, those recommendations are only valid for gateways. By repeating the attributes here, such attributes are recommended for general Internet e-mail usage. This document also gives fuller descriptions of such attributes than is given by X.400 gatewaying recommendations. Palme [Page 1] Internet draft Additional RFC 822 heading attributes March 1995 5. Obsoletes Syntax: obsoletes-field = "Obsoletes" ":" 1#msg-id The message identifiers (msg-id) use the msg-id format, as defined in RFC 822 [1]. This field identifies previous correspondence, which this message obsoletes. A user agent is expected to handle this field in much the same way as the In-Reply-To and References heading field. (a) Thus, this field does not imply any mandatory deletion of the previous correspondence. (b) User agents which provide user commands for getting from a reply to the replied-to message (or for getting from a replied-to message to its replies), may provide similar commands for getting from an obsoleting message to the obsoleted message (or for getting from an obsoleted message to its revised version). (c) User agents may normally show the recipient both the previous and the obsoleting message. If, however, both the previous and the obsoleting message have arrived, both having the same author, but the user has not yet seen either of them, a user agent may show only the obsoleting message, but also show the obsoletes-field to inform the recipient that this message obsoletes a previous message. (d) User agents might issue a warning if an obsoleting message arrives with a different author than the author of the obsoleted message. Note 1: A heading attribute with similar functionality which sometimes is seen is "Supersedes:". However, "Obsoletes:" is preferred to "Supersedes:". Safe software should understand both "Obsoletes:" and "Supersedes:" but should generate "Obsoletes:". Note 2: A similar attribute is defined in X.420 [4]. 6. Auto-Submitted Syntax: auto-submitted-field = "Auto-Submitted" ":" auto-submitted auto-submitted = "no" / "auto-generated" / "auto-replied" / "auto-forwarded" This attribute indicates whether the message was sent with or without explicit human control. This attribute, with the value "auto-replied" should be used for example for messages sent by mail servers and vacation servers in reply to incoming messages. Mail servers and vaction servers should not reply to auto-replied messages sent to them, in order to avoid loops. "no" indicates that this message was sent with explicit human action. Palme [Page 2] Internet draft Additional RFC 822 heading attributes March 1995 The absence of this attribute indicates that information is not available as to whether this message was sent with or without explicit human control. This means that also other means of prevention of loops is necessary, such as making the SMTP-sender null for messages from mail servers and vacation servers. This will be handled more fully in separate recommendations for mail servers and vacation servers. Note 1: A similar attribute is defined in X.420 [4]. 7. Expiry-date: Syntax: Expiry-date-field = "Expires" ":" date-time The expiry-date field indicates a date-time, at which this message expires. The field can be used both to limit and to extend the life of a message. User agents and servers which employ automatic purging of old messages may let this attribute influence the purging process. Note 1: This attribute is also defined, with similar meaning, in Usenet News [5] and in X.420 [4]. Note 2: Unfortunately, RFC 1327 [2] specifies this field as "Expiry- date" while Usenet News [5] specifies it as "Expires". Safe e-mail software should accept both variants, but generate the "Expires" variant. 8. References [1] D. Crocker: "Standard for the format of ARPA Internet text messages." STD 11, RFC 822, August 1982. [2] S. Hardcastle-Kille: "Mapping between X.400(1988) / ISO 10021 and RFC 822", RFC 1327 May 1992. [3] ISO/ITU: "Message Handling Systems", ISO international standard 10021, ITU recommendation X.400. [4] ISO/ITU: "Message Handling Systems, Part 7: Interpersonal Messaging System, ISO international standard 10021-7, ITU recommendation X.420. [5] M.R. Horton, R. Adams: "Standard for interchange of USENET messages", RFC 1036, December 1987. 9. Author's address Jacob Palme Phone: +46-8-16 16 67 Stockholm University/KTH Fax: +46-8-703 90 25 (not fast) Electrum 230 E-mail: jpalme@dsv.su.se S-164 40 Kista, Sweden Palme Expires September 1995 [Page 1]