I understand what you are saying, but this problem occurs when *any*
subscriber posts to the list, not just one. From what my subscribers are
reporting, this happens with every post to the list. I first checked to be
sure the list was not subscribed to itself. I also considered a subscriber
might have a forward setup that was sending list posts back to the list
address. But that would only explain one such incident, like your
misconfigured header idea, and not how this happens with every post, from
every subscriber.

The log entries I previously copied to this list were made by different
subscribers. I have a copy of the logs from that entire day, and with every
post, the duplicate error message was sent out. So, what the subscribers are
reporting is, in fact, occuring.

Any ideas?

----- Original Message ----- 
From: "F. J. Kelley" <[log in to unmask]>

look at the "Received:" headers.  One of your subscribers
mailers is misconfigured and is reposting to the list.
you will need to look these headers over very carefully
(start at the bottom), but the key is when you see your
listserver address(es) the second time (ie the mail leaves
the listserver then shows up back at the listserver as if it
were a new post).