mailing list extensions?

Hi, I'm wondering has anyone needed such a thing. I have a mailing list running on Mailman on Postfix, and only certain users can send mails. It's sort of a news list. What I want to do is, to customize each mail sent. For instance consider this. There is a user dadtabase in MySQL and I would like each mail text to start with Dear $Firstname $Lastname, .... This means each mail should be an output of a program, and I would like to do this with a list manager to avoid complications of bounces, DNs lookups etc. Is there any such extension to any list manager? TIA Oyku Gencay