Network Working Group Jacob Palme Internet Draft Stockholm University/KTH Sweden Category: Informational June 1995 Expires December 1995 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 1327, RFC 1496, RFC 1521, RFC 1766 and X.400. 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 or X.400 part, in which the attribute is defined. Common Internet Message Attributes June 1994 Palme [Page 1] Table of contents 4. Introduction 5. Use of gatewaying attributes 6. Table of attributes 6.1 Addressing information 6.2 Envelope and format information 6.3 Header fields containing mailbox names and addressable entities 6.4 Message identification and referral attributes 6.5 Other textual attributes 6.6 Attributes containing dates and times 6.7 Attributes containing other types of information 6.8 Resent-attributes 6.9 Sometimes occurring heading fields in Internet mail which are not according to standard 7. Acknowledgments 8. References 9. Author's address Appendix A: Attributes sorted by Internet RFC document in which they appear 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 1327 [4], RFC 1496 [5], RFC 1521 [6] and RFC 1766 [8]. 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 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. Information about corresponding attributes in X.400 is also given when available. 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 have but which were previously not standardized in Internet mail. Some of these attributes are obviously useful also as stand-alone Internet mail message attributes. The fact that an attribute occurs in RFC 1327 indicates that it is recommended for use in gatewaying messages between X.400 Common Internet Message Attributes June 1994 Palme [Page 1] and Internet mail, but does not necessarily mean that the attribute is recommended for messages wholly within Internet mail. However, some of these attributes may eventually get accepted also for usage within Internet mail. 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. 3. Table of attributes 3.1 Addressing information Description Internet att- Internet X.400 X400 ribute name document attribute document -----------------------+-------------+------------+------------+-------+ Original sender. Should MAIL FROM RFC 821 Originator X.411 in Internet be empty name when sending notifications, and be the list administrator when forwarding from a distribution list. Relative address to the Return-Path: RFC 821 Trace X.411 original sender along the reverse path through which the message was sent Recipient to which RCPT TO RFC 821 Recipient X.411 message is to be name delivered. 3.2 Envelope and format information Description Internet att- Internet X.400 X400 ribute name document attribute document -----------------------+-------------+------------+------------+-------+ All that is inside the DATA RFC 821 Content X.411 envelope. Trace of MTA-s which a Received: RFC 822: Trace X.411 message has passed. 4.3.2 MIME protocol version. MIME-Version: RFC 1521: 3 Mapped into RFC body part 1496 Common Internet Message Attributes June 1994 Palme [Page 1] Format of content Content-Type: RFC 1521: 4 Mapped into RFC (character set etc.) body part 1496 Coding method used in Content- RFC 1521: 5 content. Transfer- Encoding List of MTA-s passed. Path: RFC 1036: Trace X.411 2.1.6 Special Usenet News Control: RFC 1036: actions. 2.2.6 Trace of distribution DL-Expansion- RFC 1327 DL Expansion X.411 lists passed. history- History indication indication Which body part types Original- RFC 1327 Original- X.411 occur in this message. Encoded- encoded- Information- information- Types: types Special informational Message-Type: RFC 1327 Notification X.411 message. Delivery Report Controls whether this Alternate- RFC 1327 Alternate- X.411 message may be recipient: recipient- forwarded to alternate allowed recipiets such as a postmaster if delivery is not possible to the intended recipient. Default: Allowed. Whether non-delivery Prevent- RFC 1327 Originator X.411 report is wanted at NonDelivery- ReportRequest delivery error. Default Report: is to want such a report. Whether a delivery Generate- RFC 1327 Originator X.411 report is wanted at Delivery- ReportRequest successful delivery. Report: Default is not to generate such a report. Whether recipients are Disclose- RFC 1327 Disclosure- X.411 to be told the names of Recipients: of-recipients other recipients of the same message. This is Common Internet Message Attributes June 1994 Palme [Page 1] primarily an X.400 facility, such disclosure is in Internet mail done via the To:, Cc: and Bcc: heading fields. Indicates whether the Content- RFC 1327 Content-return- X.411 content of a message is Return request to be returned with non-delivery notifications. 3.3 Header fields containing mailbox names and addressable entitities Description Internet att- Internet X.400 X400 ribute name document attribute document -----------------------+-------------+------------+------------+-------+ Replacement for "From:" Reply-To: RFC 822: Reply- X.420 to which replies are to 4.4.3 recipients be sent. Not to be used as a replacement for all recipients of a reply to a multi-reci- pient message. Author, approver. From: RFC 822: Authorizing- X.420 4.4.1 users Moderator. Approved: RFC 1036: Authorizing- X.420 2.2.11 users Sender information Sender: RFC 822: Originator X.420 inside the envelope. 4.4.2 Main recipients. To: RFC 822: Primary- X.420 4.5.1 recipients Additional recipients. Cc: RFC 822: Copy- X.420 4.5.2 recipients Recipients not shown to Bcc: RFC 822: Blind-copy- X.420 other recipients. 4.5.3 recipients In Usenet News: group Newsgroups: RFC 1036: Primary- X.420 to which this article 2.1.3 Recipient was posted. In e-mail: either group to which this message was posted or group to which the Common Internet Message Attributes June 1994 Palme [Page 1] article this message is a reply-to was posted. Where group replies to Followup-To: RFC 1036: this message are to be 2.2.3 sent. Limitation on where Distribution: RFC 1036: this message can be 2.2.7 distributed. 3.4 Message identification and referral attributes Description Internet att- Internet X.400 X400 ribute name document attribute document -----------------------+-------------+------------+------------+-------+ Unique ID of this Message-ID: RFC 822: IPM X.420 message. 4.6.1 Identifier Unique ID of one body Content-ID: RFC 1521: not part of the content of 6.1 available a message. Reference to message In-Reply-To: RFC 822: Replied-to- X.420 which this message is a 4.6.2 IPM reply to. Reference to other References: RFC 822: Related-IPMs X.420 related messages. 4.6.3 Reference to previous Obsoletes: RFC 1327 Obsoleting X.420 message being corrected and replaced. 3.5 Other textual attributes Description Internet att- Internet X.400 X400 ribute name document attribute document -----------------------+-------------+------------+------------+-------+ Search keys for data Keywords: RFC 822: Heading RFC 1327 base retrieval. 4.6.4 extension Title, heading, Subject: RFC 822: Subject X.420 subject. 4.7.1 Comments on a message. Comments: RFC 822: Extra body X.420 4.7.2 part Description of a Content- RFC 1521: Heading RFC 1327 Common Internet Message Attributes June 1994 Palme [Page 1] particular body part description: 6.2 extension of a message. Organization to which Organization: RFC 1036: organization- X.520 the sender of this 2.2.8 name message belongs. Short text describing Summary: RFC 1036: Heading RFC 1327 a longer message. 2.2.10 extension??? A text string which Content- RFC 1327 Content- X.411 identifies the content identifier: identifier of a message. 3.6 Attributes containing dates and times Description Internet att- Internet X.400 X400 ribute name document attribute document -----------------------+-------------+------------+------------+-------+ The time when a Delivery- RFC 1327 Message- X.411 message was delivered Date: delivery to its recipient. time In Internet, the date Date: RFC 822: Message- X.411 when a message was 5.1 submission- written, in X.400, the time time a message was submitted. A suggested expiration Expires: RFC 1036: Expiry Date X.420 date. Can be used both 2.2.4 Indication to limit the time of an article which is not meaningful after a certain date, and to extend the storage of important articles. Time at which a message Expiry-Date: RFC 1327 Expiry Date X.420 loses its validity. Indication Latest time at which a Reply-By: RFC 1327 ReplyTime X.420 reply is requested (not Field demanded). 3.7 Attributes containing other types of information Description Internet att- Internet X.400 X400 ribute name document attribute document -----------------------+-------------+------------+------------+-------+ Common Internet Message Attributes June 1994 Palme [Page 1] Can be normal, urgent Priority: RFC 1327 Priority X.411 or non-urgent and can influence transmission speed and delivery. Size of the message. Lines: RFC 1036: Heading RFC 1327 2.2.12 extension??? Has been automatically Auto- RFC 1327 Auto- X.420 forwarded. Forwarded: Forwarded Indication Can be high, normal or Importance: RFC 1327 Importance X.420 low and is only used in the recipient client (UA). Body parts are missing. Incomplete- RFC 1327 Incomplete X.420 Copy: Copy Can include a code Language: RFC 1766 Language X.420 code for the natural RFC 1327 language used in a message, e.g. "en" for English. Can be personal, Sensitivity: RFC 1327 Sensitivity X.420 private, company- confidential or absent. The body of this Conversion: RFC 1327 Implicit- X.411 message may not be conversion- converted from one prohibited character set to another. The body of this Conversion- RFC 1327 Conversion- X.411 message may not be With-Loss: with-loss- converted from one prohibited character set to another if information will be lost. Can be used in Internet Discarded- RFC 1327 Extensions X.420 mail to indicate X.400 X400-IPMS- Field extensions which Extensions: could not be mapped to Internet mail Discarded- RFC 1327 Extensions X.420 format. X400-MTS- Field Common Internet Message Attributes June 1994 Palme [Page 1] Extensions: 3.8 Resent-attributes Description Internet att- Internet X.400 X400 ribute name document attribute document -----------------------+-------------+------------+------------+-------+ When forwarding a Resent-Reply- RFC 822, Embedded X.420 message, attributes To:, Resent- C.3.3 message referring to the From:, Resent- bodies forwarding, not to the Sender:, should be original message. Resent-From:, used for Resent-Date:, forwarding. Note: MIME specifies Resent-To:, another way of resen- Resent-cc:, ding messages, using Resent-bcc:, the "Message" Content- Resent- Type. Message-ID: 3.9 Sometimes occurring heading fields in Internet mail which are not according to standard This chapter does not include a complete collection of all heading attributes, such a list would be much longer. It contains a few attributes which occur frequently and for which an explanation may be useful here. Description Internet att- Internet X.400 X400 ribute name document attribute document -----------------------+-------------+------------+------------+-------+ Inserted by Sendmail Apparently- RFC 1211 in certain cases, lis- to: ting recipients deriv- ed from the envelope into the message heading. This behavi- or is not quite pro- per, MTA-s should not modify headings (ex- cept inserting Reci- eved lines), and it can in some cases cause Bcc recipients to be wrongly divulged. Inserted by certain Content- mailers to indicate length: the size in bytes of the message text. Can Common Internet Message Attributes June 1994 Palme [Page 1] cause several robust- ness and interoperabi- lity problems and is not recommended. Pre-MIME way of indi- Encoding: RFC 1154 cating encoding format in message. Address to which Errors-To:, notifications are to Return- be sent. Internet Receipt-To: standards recommend, however, the use of RCPT TO and Return- Path, not Errors-To, for this. Fax number of the Fax:, X.520 originator. Telefax: Name of file in which a Fcc: copy of this message is stored. Information about the Mail-System- client software of the Version:, originator. Mailer: See Organization. Organisation: organization X.520 -name Information about the Originating- client software of the Client: originator. Phone number of the Phone: O/R X.420 originator. Descriptor, (X.520) telephone- number Used in Usenet News Supersedes: in similar ways to the "Obsoletes" attri- bute described earlier in this document. 4. Acknowledgments Harald Tveit Alvestrand and several other people has helped me with compiling this list. I alone take responsibility for any errors which may be in the list. Common Internet Message Attributes June 1994 Palme [Page 1] An earlier version of this list has been published as part of [7]. 5. References [1] J. Postel: "Simple Mail Transfer Protocol", STD 10, RFC 821, August 1982. [2] D. Crocker: "Standard for the format of ARPA Internet text messages." STD 11, RFC 822, August 1982. [3] M.R. Horton, R. Adams: "Standard for interchange of USENET messages", RFC 1036, December 1987. [4] S. Hardcastle-Kille: "Mapping between X.400(1988) / ISO 10021 and RFC 822", RFC 1327 May 1992. [5] H. Alvestrand & 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. [6] 1521 N. Borenstein & N. Freed: "MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies", RFC 1521, September 1993. [7] J. Palme: "Electronic Mail", Artech House publishers, London- Boston January 1995. [8] H. Alvestrand: "Tags for the Identification of Languages", RFC 1766, February 1995. 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 ------- Common Internet Message Attributes June 1994 Palme [Page 1] 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 RFC 1036 -------- Approved Control Distribution Expires Followup-To Lines Newsgroups Organization Path Summary RFC 1327 -------- Alternate-recipient Auto-Forwarded Autoforwarded Content-identifier Content-Return Conversion Conversion-With-Loss Delivery-Date Common Internet Message Attributes June 1994 Palme [Page 1] 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 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 Common Internet Message Attributes June 1994