> one of the folks on our listserv is saying that he's receiving 5 copies of our
> newsletter at a time. when i look at the list of subscribers, his email
> address only appears once, and when i delete and resubsribe his account, that
> doesn't seem to help. any ideas?

If you take two different copies of the same message and compare the Received
headers, the point at which the timestamps begin to differ tells you the
point at which the duplication occurred.  Note that the Received headers
have to be read from the bottom up.  The topmost Received header is the
most recent.