rfc2076.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

Network Working Group                                          J. Palme
Request for Comments: 2076                     Stockholm University/KTH
Category: Informational                                   February 1997


                    Common Internet Message Headers

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Abstract

   This memo contains a table of commonly occurring headers in headings
   of e-mail messages. The document compiles information from other RFCs
   such as RFC 822, RFC 1036, RFC 1123, RFC 1327, RFC 1496, RFC 1521,
   RFC 1766, RFC 1806, RFC 1864 and RFC 1911. A few commonly occurring
   headers which are not defined in RFCs are also included. For each
   header, the memo gives a short description and a reference to the RFC
   in which the header is defined.

Table of contents
   1. Introduction..............................................  2
   2. Use of gatewaying headers.................................  3
   3. Table of headers..........................................  3
        3.1 Phrases used in the tables..........................  3
        3.2 Trace information...................................  5
        3.3 Format and control information......................  5
        3.4 Sender and recipient indication.....................  6
        3.5 Response control....................................  9
        3.6 Message identification and referral headers......... 11
        3.7 Other textual headers............................... 12
        3.8 Headers containing dates and times.................. 13
        3.9 Quality information................................. 13
        3.10 Language information............................... 14
        3.11 Size information................................... 14
        3.12 Conversion control................................. 15
        3.13 Encoding information............................... 15
        3.14 Resent-headers..................................... 16
        3.15 Security and reliability........................... 16
        3.16 Miscellaneous...................................... 16
   4. Acknowledgments........................................... 18







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   5. References................................................ 18
   6. Author's Address.......................................... 20
   Appendix A:
   Headers sorted by Internet RFC document in which they appear. 21
   Appendix B:
   Alphabetical index........................................... 25

1. Introduction

   Many different Internet standards and RFCs define headers which may
   occur on Internet Mail Messages and Usenet News Articles. The
   intention of this document is to list all such headers in one
   document as an aid to people developing message systems or interested
   in Internet Mail standards.

   The document contains all headers which the author has found in the
   following Internet standards: , RFC 822 [2], RFC 1036 [3], RFC 1123
   [5], RFC 1327 [7], RFC 1496 [8], RFC 1521 [11], RFC 1766 [12], RFC
   1806 [14], RFC 1864[17] and RFC 1911[20]. Note in particular that
   heading attributes defined in PEM (RFC 1421-1424) and MOSS (RFC 1848
   [16]) are not included. PEM and MOSS headers only appear inside the
   body of a message, and thus are not headers in the RFC 822 sense.
   Mail attributes in envelopes, i.e. attributes controlling the message
   transport mechanism between mail and news servers, are not included.
   This means that attributes from SMTP [1], UUCP [18] and NNTP [15] are
   mainly not covered either. Headings used only in HTTP [19] are not
   included yet, but may be included in future version of this memo. A
   few additional headers which often can be found in e-mail headings
   but are not part of any Internet standard are also included.

   For each header, the document gives a short description and a
   reference to the Internet standard or RFC, in which they are defined.

   The header names given here are spelled the same way as when they are
   actually used. This is usually American but sometimes English
   spelling.  One header in particular, "Organisation/Organization",
   occurs in e-mail headers sometimes with the English and other times
   with the American spelling.

   The following words are used in this memo with the meaning specified
   below:

   heading           Formatted text at the top of a message, ended by a
                     blank line

   header = heading  One field in the heading, beginning with a field
   field             name, colon, and followed by the field value(s)




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   It is my intention to continue updating this document after its
   publication as an RFC. The latest version, which may be more up-to-
   date (but also less fully checked out) will be kept available for
   downloading from URL
   http://www.dsv.su.se/~jpalme/ietf-mail-attributes.pdf.

   Please e-mail me (Jacob Palme <[e-mail]>) if you have noted
   headers which should be included in this memo but are not.

2. Use of gatewaying headers

   RFC 1327 defines a number of new headers in Internet mail, which are
   defined to map headers which X.400 has but which were previously not
   standardized in Internet mail. The fact that a header occurs in RFC
   1327 indicates that it is recommended for use in gatewaying messages
   between X.400 and Internet mail, but does not mean that the header is
   recommended for messages wholly within Internet mail. Some of these
   headers may eventually see widespread implementation and use in
   Internet mail, but at the time of this writing (1996) they are not
   widely implemented or used.

   Headers defined only in RFC 1036 for use in Usenet News sometimes
   appear in mail messages, either because the messages have been
   gatewayed from Usenet News to e-mail, or because the messages were
   written in combined clients supporting both e-mail and Usenet News in
   the same client. These headers are not standardized for use in
   Internet e-mail and should be handled with caution by e-mail agents.

3. Table of headers

3.1 Phrases used in the tables

   "not for general        Used to mark headers which are defined in RFC
   usage"                  1327 for use in messages from or to Internet
                           mail/X.400 gateways. These headers have not
                           been standardized for general usage in the
                           exchange of messages between Internet mail-
                           based systems.













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   "not standardized       Used to mark headers defined only in RFC 1036
   for use in e-mail"      for use in Usenet News. These headers have no
                           standard meaning when appearing in e-mail,
                           some of them may even be used in different
                           ways by different software. When appearing in
                           e-mail, they should be handled with caution.
                           Note that RFC 1036, although generally used as
                           a de-facto standard for Usenet News, is not an
                           official IETF standard or even on the IETF
                           standards track.

   "non-standard"          This header is not specified in any of
                           referenced RFCs which define Internet
                           protocols, including Internet Standards, draft
                           standards or proposed standards. The header
                           appears here because it often appears in e-
                           mail or Usenet News. Usage of these headers is
                           not in general recommended. Some header
                           proposed in ongoing IETF standards development
                           work, but not yet accepted, are also marked in
                           this way.

   "discouraged"           This header, which is non-standard, is known
                           to create problems and should not be
                           generated. Handling of such headers in
                           incoming mail should be done with great
                           caution.

   "controversial"         The meaning and usage of this header is
                           controversial, i.e. different implementors
                           have chosen to implement the header in
                           different ways. Because of this, such headers
                           should be handled with caution and
                           understanding of the different possible
                           interpretations.

   "experimental"          This header is used for newly defined headers,
                           which are to be tried out before entering the
                           IETF standards track. These should only be
                           used if both communicating parties agree on
                           using them. In practice, some experimental
                           protocols become de-facto-standards before
                           they are made into IETF standards.








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3.2 Trace information

   Used to convey the information       Return-Path:   RFC 821,
   from the MAIL FROM envelope                         RFC 1123: 5.2.13.
   attribute in final delivery, when
   the message leaves the SMTP
   environment in which "MAIL FROM"
   is used.

   Trace of MTAs which a message has    Received:      RFC 822: 4.3.2,
   passed.                                             RFC 1123: 5.2.8.

   List of MTAs passed.                 Path:          RFC 1036: 2.1.6,
                                                       only in Usenet
                                                       News, not in e-
                                                       mail.

   Trace of distribution lists          DL-Expansion-  RFC 1327, not for
   passed.                              History-       general usage.
                                        Indication:

3.3 Format and control information

   An indicator that this message is    MIME-Version:  RFC 1521: 3.
   formatted according to the MIME
   standard, and an indication of
   which version of MIME is
   utilized.

   Special Usenet News actions only.    Control:       RFC 1036: 2.1.6,
                                                       only in Usenet
                                                       News, not in e-
                                                       mail.

   Special Usenet News actions and a    Also-Control:  son-of-RFC1036
   normal article at the same time.                    [21], non-
                                                       standard, only in
                                                       Usenet News, not
                                                       in e-mail

   Which body part types occur in       Original-      RFC 1327, not for
   this message.                        Encoded-       general usage.
                                        Information-
                                        Types:







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   Controls whether this message may    Alternate-     RFC 1327, not for
   be forwarded to alternate            Recipient:     general usage.
   recipients such as a postmaster
   if delivery is not possible to
   the intended recipient. Default:
   Allowed.

   Whether recipients are to be told    Disclose-      RFC 1327, not for
   the names of other recipients of     Recipients:    general usage.
   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: headers.

   Whether a MIME body part is to be    Content-       RFC 1806,
   shown inline or is an attachment;    Disposition:   experimental
   can also indicate a suggested
   filename for use when saving an
   attachment to a file.

3.4 Sender and recipient indication

   Authors or persons taking            From:          RFC 822: 4.4.1,
   responsibility for the message.                     RFC 1123: 5.2.15-
                                                       16, 5.3.7,
   Note difference from the "From "                    RFC 1036 2.1.1
   header (not followed by ":")
   below.


   (1) This header should never         From           not standardized
   appear in e-mail being sent, and                    for use in e-mail
   should thus not appear in this
   memo. It is however included,
   since people often ask about it.











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   This header is used in the so-
   called Unix mailbox format, also
   known as Berkely mailbox format
   or the MBOX format. This is a
   format for storing a set of
   messages in a file. A line
   beginning with "From " is used to
   separate successive messages in
   such files.

   This header will thus appear when
   you use a text editor to look at
   a file in the Unix mailbox
   format. Some mailers also use
   this format when printing
   messages on paper.

   The information in this header
   should NOT be used to find an
   address to which replies to a
   message are to be sent.

   (2) Used in Usenet News mail         From           RFC 976: 2.4 for
   transport, to indicate the path      or             use in Usenet News
   through which an article has gone    >From
   when transferred to a new host.

   Sometimes called "From_" header.

   Name of the moderator of the         Approved:      RFC 1036: 2.2.11,
   newsgroup to which this article                     not standardized
   is sent; necessary on an article                    for use in e-mail.
   sent to a moderated newsgroup to
   allow its distribution to the
   newsgroup members. Also used on
   certain control messages, which
   are only performed if they are