Subject: Re: [Fwd: Apologies for multiple messages (Please Help!)]
From: Herb Maeder <[email-masked]>
To: [email-masked]
Cc: [email-masked]
Date: Fri, 24 Oct 2008 10:04:56 -0700
List-Id: <cygwin.cygwin.com>

On 24 Oct 2008 10:30:08 +0200, Corinna Vinschen wrote:
> we have a strange mail duplication here on the cygwin ML.  The
> mail with Message ID <[email-masked]>
> is duplicated over and over again.  Could something on sourceware
> be the culprit?

Now that is interesting!  I see the message come back to me with no
Message-ID in the headers (sample included below, with '@' and '.'
replaced to protect the innocent).

I have a theory as to what's going on...

I believe that adding the Message-ID field is the responsibility of the
MUA.  But some mail servers add a Message-ID if it is missing.  I just
verified that my MUA was not creating the Message-ID field, and I'm
guessing that one got added somewhere along the way to Corinna's mailbox.

I don't think that the missing Message-ID is the root cause of the mail
duplication problem.  But I do believe that the missing Message-ID causes
the workaround to the problem to fail.  I'm guessing that the
sourceware.org server may detect and prevent duplicated messages based on 
the Message-ID field.  But since there wasn't one in my message, that
mechanism did not work.

(I've got a hunch that the root cause may be some miscommunication between
the servers due to timeouts or something, but I have no way to verify
that).

In any case, if my guess about the misssing Message-ID is correct, then
I believe that a few of things should be done:

  1) I should make sure that my MUA generates the Message-ID field on
     outgoing messages.  I believe that I have fixed this now (and this
     message should have a "@maeder.org" Message-ID).

  2) If the cygwin mail server is truly depending on Message-ID to stop
     this message duplication, it should somehow ensure that it is always
     there.  One option would be to prevent posts to the list that are 
     missing the Message-ID field (with some reasonable return error
     message to the sender).  NOTE: I'm not sure if generating a Message-ID 
     field on the cygwin mail server would work (that might just add 
     a unique Message-ID on each duplicated message, I'm not sure).

  3) Determine and fix the root of the duplication problem (though I'm not 
     sure how feasible this would really be).

I think most modern MUA's add the Message-ID field, but it is not a strict
requirement.  Implementing something for 2) above may help avoid the
duplication problem for mail sent from misconfigured and/or old school mail
clients (nmh in my case).

How to stop the still repeating evil message?  I still haven't a clue...

Herb.

From cygwin-return-145237-maeder-cygml=maeder DOT org AT cygwin DOT com Thu Oct 23 20:44:41 2008
To: cygwin AT cygwin DOT com
From: Herb Maeder <maeder-cygml AT maeder DOT org>
Subject: Re: Compile time Local Cygwin vs. VMware session on same system
Date: Thu, 23 Oct 2008 13:43:30 -0700
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