C
Cedders
Outlook 2007 will sometimes create a Message-ID header that is illegal
under RFC 2822, and in a format that has previously been mostly
associated with spam. I noticed this when Outlook users with email
addresses in the form (e-mail address removed) complained their outgoing
messages were being marked as spam, and the bug only seems to trigger
when the local part of the From address contains a dot. We then see
things like:
From: "Mary Jones" <[email protected]>
To: (e-mail address removed)
Date: Mon, 27 Jul 2009 10:17:06 +0100
Message-ID: <001601ca0e9b$e4b53100$ae1f9300$@[email protected]>
MIME-Version: 1.0
RFC 2822 specifies:
msg-id = [CFWS] "<" id-left "@" id-right ">" [CFWS]
id-left = dot-atom-text / no-fold-quote / obs-id-left
id-right = dot-atom-text / no-fold-literal / obs-id-
right
and "@" is not a permitted character in an atom. It appears Outlook
2007 is misidentifying the domain part from the From address, which
Outlook version 11 never did.
There is discussion about a workaround planned for SpamAssassin at
https://issues.apache.org/SpamAssassin/show_bug.cgi?id=5707
but this pattern may also be a spam cue in MS's own junk mail filters.
under RFC 2822, and in a format that has previously been mostly
associated with spam. I noticed this when Outlook users with email
addresses in the form (e-mail address removed) complained their outgoing
messages were being marked as spam, and the bug only seems to trigger
when the local part of the From address contains a dot. We then see
things like:
From: "Mary Jones" <[email protected]>
To: (e-mail address removed)
Date: Mon, 27 Jul 2009 10:17:06 +0100
Message-ID: <001601ca0e9b$e4b53100$ae1f9300$@[email protected]>
MIME-Version: 1.0
RFC 2822 specifies:
msg-id = [CFWS] "<" id-left "@" id-right ">" [CFWS]
id-left = dot-atom-text / no-fold-quote / obs-id-left
id-right = dot-atom-text / no-fold-literal / obs-id-
right
and "@" is not a permitted character in an atom. It appears Outlook
2007 is misidentifying the domain part from the From address, which
Outlook version 11 never did.
There is discussion about a workaround planned for SpamAssassin at
https://issues.apache.org/SpamAssassin/show_bug.cgi?id=5707
but this pattern may also be a spam cue in MS's own junk mail filters.