On Thu, 02 Oct 1997 15:12:22 EDT, you said:
> I have had a report from a list owner that messages have been returned to
> subscribers with the following explanation.  The subscriber did NOT post
> the message twice.  What causes this to happen?  Thank you.

Usually, this is the result of a broken mailer - sometimes, mail gets
duplicated because of the following scenario:

1) Sending system contacts receiving system, starts sending the mail.
2) Receiving system opens a queue file, and starts spooling the mail.
3) All the mail is sent over, and during the final exchanges, Something Bad
happens (either the network link drops, or the receiving system 4xx's the
mail, etc).
4a) Broken receiving system goes ahead and sends the mail along ANYHOW,
even after having sent a 4xx reply on the SMTP transaction.  Later on,
sending host tries again, creating a duplicate.
4b) Network crash/hang before the sending system gets a '250 OK' back saying
that the mail is accepted/queued (even though the receiving system SENT it).
Receiving system processes it (like the 250 says it will), but sending system
retries later because it was never definitively told the mail was received.

Does any of that explain what you are seeing?
--
                                Valdis Kletnieks
                                Computer Systems Senior Engineer
                                Virginia Tech