[Mailman-Users] Mailman + Sendmail

[Rich West]

I've had mailman running for years and have only recently started having 
some delivery problems with it.  I originally chalked it up to a 
particular set of users within the one list that I am on (we host a 
bunch of lists for others), but, after some investigation, I have been 
unable to narrow down the source of the problem.

Essentially, we have users A, B, C, and D.  A&B have accounts local to 
the mailman/mail server and C&D have accounts elsewhere.  Now, when any 
user emails to the list, mailman receives the message, then spawns off 4 
(right now, I have "nodupes" deselected for everyone) messages in the 
sendmail queue.

If sendmail had just recently been started (aka: within the past 5 
minutes), the message will go through just fine.

However, in most cases, the messages (all with the same message ID) hang 
in the queue forever.. or, at least, until sendmail gets restarted at 
which time all of the messages get delivered.

At this point, one would say "It's sendmail", as did I.  I dug, and dug, 
but could not repeat the scenario without mailman in the loop.  I could 
send email to each user directly, I could create an alias called 'test' 
with each of the users in the alias, and then have any one of them mail 
to "test" to have it successfully send that out to everyone.

I looked in the logs on mailman, and saw nothing out of the ordinary.

I'm pretty much at a loss as to where else to turn.  I tried deleting 
the list and re-adding it, I tried deleting the list and creating one 
under a different name.. I tried upgrading to Mailman 2.1.6.  So far, 
everything is consistent.

I was thinking of trying to set mailman to send only one message per 
connection or something just to see if the other messages would process 
and just leave the hanging ones out there (not sure how to set this, 
though).

I searched the archives, too, but didn't have much luck there as I was 
not sure how to narrow down the search enough (I couldn't come up with 
good search terms).

Any ideas/help/pointers would be much appreciated!

Thanks!
-Rich