Need a different Discussion List

Hi, I have been using the Mailman discussion list (from the one click install) on my site. It’s really not what I want.

I have a membership fee based site where user’s sign up and pay each year. So, on July 31, 06 at midnight my users will all expire. They can start signing up/updating memberships on August 1 at 12:01am.

I need a discussion list that can check the member’s database and see if expired = no, then allow that user access to the list and new users can sign up. If expired = yes then they cannot be a part of the list.

I have googled and found nothing that seems useable. Is there anyone here that knows of a good list or another recommendation.

Much Much appreciated.