[CentOS] Trouble with Mailman

I have set up Mailman on a virtual private server from 1and1 running 
Centos, though I can't tell which version. The system has 2 GB of 
memory. Mailman is receiving posts, but it is not sending them out to 
everybody. It is also getting some out-of-memory errors. The server is 
also runing Plesk for Web hosting. Something on the server is leaking 
memory. When first booted it has nearly 1.5 GB of free memory. Now this 
is down to .75 GB. Any hints will be appreciated.

Thanks,
-- 
John J. Boyer; President, Chief Software Developer
Abilitiessoft, Inc.
http://www.abilitiessoft.com
Madison, Wisconsin USA
Developing software for people with disabilities