usefor-article-07 May 2002

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 definition of no-fold-quote
   and no-fold-literal.

      header             =/ Message-ID-header
      Message-ID-header  = "Message-ID" ":" SP Message-ID-content
                    *( ";" other-parameter )
      Message-ID-content = msg-id
      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: 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 NEVER
   reused (either in 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.
        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-06/Message-ID.out          November 2001
+++ ../usefor-article-07/Message-ID.out          May 2002
@@ -1,38 +1,58 @@
 5.3.  Message-ID
 
-   The Message-ID header contains the article's message identifier, a
+   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 definition of no-fold-quote
    and no-fold-literal.
 
+      header             =/ Message-ID-header
+      Message-ID-header  = "Message-ID" ":" SP Message-ID-content
+                    *( ";" other-parameter )
       Message-ID-content = msg-id
       id-left            = dot-atom-text / no-fold-quote
       id-right           = dot-atom-text / no-fold-literal
-      no-fold-quote      = DQUOTE *( strict-qtext / strict-quoted-pair )
+      no-fold-quote      = DQUOTE
+                    *( strict-qtext / "\\" / "\" DQUOTE )
+                    qspecial
+                    *( strict-qtext / "\\" / "\" DQUOTE )
                     DQUOTE
-      no-fold-literal    = DQUOTE *( dtext / strict-quoted-pair ) DQUOTE
+      qspecial           = "(" / ")" /        ; same as specials except
+                 "<" / ">" /        ; "\" and DQUOTE quoted
+                 "[" / "]" /
+                 ":" / ";" /
+                 "@" / "\\" /
+                 "," / "." /
+                 "\" DQUOTE
+      no-fold-literal    = "[" *( dtext / "\[" / "\]" / "\\" ) "]"
 
-   A msg-id MUST NOT contain any SP within any strict-quoted-pair.  The
-   msg-id MUST NOT be more than 250 octets in length.
+   The msg-id MUST NOT be more than 250 octets in length.
 
-        NOTE: The syntax ensures that a msg-id is restricted to pure
-        US-ASCII, and is thus a strict subset of that defined by [RFC
-        2822].  The exclusion of SP is to ensure compatibility with
-        existing software.  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 '>'.
+        NOTE: 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 '>'.
 
-   Following the provisions of [RFC 2822], an agent generating an
-   article's message identifier MUST ensure that it is unique and that
-   it is NEVER reused (either in 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 recognise that same message identifier
-   wherever it subsequently reappears.
+   An agent generating an article's message identifier MUST ensure that
+   it is unique (as also required in [RFC 2822]) and that it is NEVER
+   reused (either in 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.
+        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,