usefor-article-09 February 2003

5.3.  Message-ID

   The Message-ID-header contains the article's message identifier, a
   unique identifier distinguishing the article from every other
   article. The content syntax makes use of syntax defined in [RFC
   2822], subject to the following revised definitions of msg-id, no-
   fold-quote and no-fold-literal.

      header             =/ Message-ID-header
      Message-ID-header  = "Message-ID" ":" SP Message-ID-content
      Message-ID-content = [FWS] msg-id [FWS]
      msg-id             = "<" id-left "@" id-right ">"
      id-left            = dot-atom-text / no-fold-quote
      id-right           = dot-atom-text / no-fold-literal
      no-fold-quote      = DQUOTE
                    *( strict-qtext / "\\" / "\" DQUOTE )
                    qspecial
                    *( strict-qtext / "\\" / "\" DQUOTE )
                    DQUOTE
      qspecial           = "(" / ")" /        ; same as specials except
                 "<" / ">" /        ; "\" and DQUOTE quoted
                 "[" / "]" /
                 ":" / ";" /
                 "@" / "\\" /
                 "," / "." /
                 "\" DQUOTE
      no-fold-literal    = "[" *( dtext / "\[" / "\]" / "\\" ) "]"

   The msg-id MUST NOT be more than 250 octets in length.

        NOTE: Observe that, in contrast to the corresponding header in
        [RFC 2822], the syntax does not allow comments within the
        Message-ID-header; this is to simplify processing by relaying
        and serving agents and to ensure interoperability with existing
        implementations.
        The restriction to strict-qtext ensures that no UTF8-xtra-char
        can appear. Msg-ids as defined here are a "normalized" subset of
        those defined by [RFC 2822], ensuring that no string of
        characters is quoted unless strictly necessary (it must contain
        at least one qspecial) and no single character is prefixed by a
        "\" in the form of a quoted-pair unless strictly necessary, and
        moreover there is no possibility for WSP to occur, whether
        quoted or not. The length restriction ensures that systems which
        accept message identifiers as a parameter when retrieving an
        article (e.g. [NNTP]) can rely on a bounded length. Observe that
        msg-id includes the '<' and '>'.

   An agent generating an article's message identifier MUST ensure that
   it is unique (as also required in [RFC 2822]) and that it is chosen
   in such a way that it will NEVER be applied to any other Netnews
   article or Email message. However, an article emailed (without
   encapsulation) to a moderator (8.2.2 and 8.7) or gatewayed into some
   other medium (8.8.1) SHOULD retain the same message identifier
   throughout its travels so long as it remains recognizably the same
   article.

   Even though commonly derived from the domain name of the originating
   site (and domain names are case-insensitive), a message identifier
   MUST NOT be altered in any way during transport, or when copied (as
   into a References-header), and thus a simple (case-sensitive)
   comparison of octets will always suffice to recognize that same
   message identifier wherever it subsequently reappears.

        NOTE: These requirements are to be contrasted with those of the
        un-normalized msg-ids defined by [RFC 2822], which may perfectly
        legitimately become normalized (or vice versa) during transport
        or copying in email systems.

        NOTE: Some old software may treat message identifiers that
        differ only in case within their id-right part as equivalent,
        and implementors of agents that generate message identifiers
        should be aware of this.

--- ../usefor-article-08/Message-ID.out          August 2002
+++ ../usefor-article-09/Message-ID.out          February 2003
@@ -8,7 +8,6 @@
 
       header             =/ Message-ID-header
       Message-ID-header  = "Message-ID" ":" SP Message-ID-content
-                    *( ";" other-parameter )
       Message-ID-content = [FWS] msg-id [FWS]
       msg-id             = "<" id-left "@" id-right ">"
       id-left            = dot-atom-text / no-fold-quote
@@ -34,7 +33,6 @@
         Message-ID-header; this is to simplify processing by relaying
         and serving agents and to ensure interoperability with existing
         implementations.
-
         The restriction to strict-qtext ensures that no UTF8-xtra-char
         can appear. Msg-ids as defined here are a "normalized" subset of
         those defined by [RFC 2822], ensuring that no string of
@@ -49,13 +47,19 @@
 
    An agent generating an article's message identifier MUST ensure that
    it is unique (as also required in [RFC 2822]) and that it is chosen
-   in such a way that it will NEVER recur in either Netnews or Email.
-   Moreover, even though commonly derived from the domain name of the
-   originating site (and domain names are case-insensitive), a message
-   identifier MUST NOT be altered in any way during transport, or when
-   copied (as into a References-header), and thus a simple (case-
-   sensitive) comparison of octets will always suffice to recognize that
-   same message identifier wherever it subsequently reappears.
+   in such a way that it will NEVER be applied to any other Netnews
+   article or Email message. However, an article emailed (without
+   encapsulation) to a moderator (8.2.2 and 8.7) or gatewayed into some
+   other medium (8.8.1) SHOULD retain the same message identifier
+   throughout its travels so long as it remains recognizably the same
+   article.
+
+   Even though commonly derived from the domain name of the originating
+   site (and domain names are case-insensitive), a message identifier
+   MUST NOT be altered in any way during transport, or when copied (as
+   into a References-header), and thus a simple (case-sensitive)
+   comparison of octets will always suffice to recognize that same
+   message identifier wherever it subsequently reappears.
 
         NOTE: These requirements are to be contrasted with those of the
         un-normalized msg-ids defined by [RFC 2822], which may perfectly