[Mailman-Users] Eliminating Duplicate Postings

[Barry Finkel]

A few days ago in one of my Mailman 2.1.9 lists, a posting at 7AM
was distributed to the members without problem.  The mail is addressed
to two lists, and both lists received, archived, and distributed the
mail.

At 5PM one of the recipients must have forwarded the mail back to
the lists.  The RFC 822/2822 mail headers have the same

     Return-Path:
     From:
     To:

lines as the original mail, and in addition there is a header line

     X-BeenThere: ...

for one of the lists (i.e., the list to which this recipient is
subscribed).  The mail reached Mailman.  I see in the Postfix
logs

     status=bounced (mail forwarding loop for LISTNAME)

I assume this is because there already is an X-BeenThere line for that
list.  The mail to the other Mailman list was accepted by Mailman
and redistributed to that list.  But I do not see a copy of the
second distribution in the archives.  I can see why Mailman accepted
the 5PM mail - it had an authorized "From:" address.  But why was
the mail not archived?  Because it was a duplicate mail?  

I would expect to have the archives contain a record of what was
sent.  Should Mailman have caught the duplicate posting?

I have not been in contact with the recipient to determine exactly what
he/she did.  I would like to prevent this from occurring in the future.
----------------------------------------------------------------------
Barry S. Finkel
Computing and Information Systems Division
Argonne National Laboratory          Phone:    +1 (630) 252-7277
9700 South Cass Avenue               Facsimile:+1 (630) 252-4601
Building 222, Room D209              Internet: BSFinkel at anl.gov
Argonne, IL   60439-4828             IBMMAIL:  I1004994