[Mailman-Users] Messages discarded by ISP

[Matthew Thompson]

One thing I would test is to send a message from one of the other
addresses on the list (say the gmail account) and see if the message
makes it to all of the recipients.  

I had a problem that sounds a lot like yours.  The cause was the ISP
filtering out incoming messages with a from address with their domain
name.  If someone from a different domain sent a message, it all worked
fine.

If that is the cause of your problem, I have a custom handler that I
could probably clean up and send to you that would get you most of the
way to fixing the issue.

An even simpler fix is to make the list anonymous but that has it's own
list of drawbacks.

Good luck!

-Matt