> I think you may have that backwards -- most MUAs (mail clients) add > the Message-ID: header (Eudora, Outlook, etc.). I've never heard of > anti-spam software looking for a preexisting Message-ID: header, but > some anti-spam software will look for a missing Message-ID: header.
This is rapidly going to turn into an OT RFC debate, but here goes. I'mof the opinion that MUAs that add a Message-ID: that cannot be guaranteed globally unique as advised in 2822 are more out of compliance than MUAs that don't add one at all, since Message-ID:'s are SHOULDs, but their uniqueness is a MUST if they are provided. 2822 specifies the following nomenclature: > The message identifier (msg-id) itself MUST be a globally unique > identifier for a message. The generator of the message identifier > MUST guarantee that the msg-id is unique. There are several > algorithms that can be used to accomplish this. Since the msg-id has > a similar syntax to angle-addr (identical except that comments and > folding white space are not allowed), a good method is to put the > domain name (or a domain literal IP address) of the host on which > the message identifier was created on the right hand side of the > "@", and put a combination of the current absolute date and time > along with some other currently unique (perhaps sequential) > identifier available on the system (for example, a process id > number) on the left hand side...Though other algorithms will work, > it is RECOMMENDED that the right hand side contain some domain > identifier (either of the host itself or otherwise) such that the > generator of the message identifier can guarantee the uniqueness of > the left hand side within the scope of that domain. But looking at the Message-ID:'s gen'd by a few representative MUAs, we see substantial divergence from GUID: > Mailer: Eudora 5.1 > Generating host: panda.declude.com > Message-ID: <[EMAIL PROTECTED]> > > Mailer: The Bat! 1.53 > Generating host: bsnyc-gw02.broadleaf.net > Message-ID: <[EMAIL PROTECTED]> > > Mailer: Pegasus 4.01 > Generating host: rhettspencer.141.com > Message-ID: <3CE67711.15946.1A25698C@localhost> > > Mailer: Outlook 2000, IMO mode > Generating host: bgctwld.tonerworld.com > Message-ID: <[EMAIL PROTECTED]> > > Mailer: Outlook 2000, CWS mode > Generating host: lcomes.vaneck.com > Message-ID: <007701c1fffc$612dfd90$6f010059@LCOMES> > > Mailer: Outlook Express 6 > Generating host: samurai.videotron.ca > Message-ID: <00b401c1fdbe$e29a2150$6e188242@SAMURAI> > > Mailer: Mozilla 4.79 > Generating host: sitofox.it > Message-ID: <[EMAIL PROTECTED]> Of course, much more research would be necessary to determine the full algorithm used by each MUA in each situation. But I think the gist of what I'm getting at is above. Only Mozilla uses a safe GUID algorithm, whereas the M$ products use the unqualified hostname (not unique), Pegasus uses localhost (definitely not unique), The Bat! uses the local domain name as a hostname (which it is not obliged to do, as it can't assume uniqueness on the part of a remote machine), and Eudora seems to use the remote SMTP server name (which, according to programming principles, is not legit unless GUID generation is truly distributed). Now, of course, there are RFC 2821 issues with a publicly referenced MTA (the definition of which can be debated in mutihomed/NAT environments) adding headers once a message is in transit. But I'm more comfortable with a GUID algorithm that uses a known unique constant, even if that means the MTA has to do it. Of course, I was wrong about the anti-spam measures. -Sandy > The "Message-ID:" field provides a unique message identifier that > refers to a particular version of a particular message. The > uniqueness of the message identifier is guaranteed by the host that > generates it (see below). This message identifier is intended to be > machine readable and not necessarily meaningful to humans. A message > identifier pertains to exactly one instantiation of a particular > message; subsequent revisions to the message each receive new message > identifiers. I'm not encouraging the lack Please visit http://www.ipswitch.com/support/mailing-lists.html to be removed from this list. An Archive of this list is available at: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Please visit the Knowledge Base for answers to frequently asked questions: http://www.ipswitch.com/support/IMail/
