Thanks Barry.
We figured out our problem, which I think is different from what you are talking about.
Details:
our aborted upgrade to mailman 2.0rc1 left behind a few files.
somehow these files interfered with normal exception handling.
when mailman decides a message must be held for moderation, it sends the user a "held for moderation" message and raises an special exception.
but this exception was no longer handled appropriately, so it got passed all the way up to qmail.
qmail therefore thought the delivery was a failure, and would schedule another attempt. And so on.
Deleting the leftover files from 2.0rc1 seems to have fixed it.
This was certainly a very bizarre interaction... I'm not sure if a patch to mailman is appropriate.
Perhaps the action of sending the 'held for moderation', or similar, email, should be deferred as late as possible. That way if there are problems, at least it won't be sent out an infinite number of times. Or alternatively, close the connection to the MTA sooner.
-- Neil Kandalgaonkar NeilK@ActiveState.com Web Application Developer, ActiveState