dpkg -r mailman should uninstall mailman, but leave your configuriations 
alone. dpkg --purge mailman would blow everything away. But it would still be 
in your best interests to back up your configs first.  

-- 
Andrew S. Zbikowski | http://www.ringworld.org/~zibby 
Bender: You just think that robots are machines built by humans to make
their lifes easier. 				Fry: Well, aren't they? 
Bender: I've never made anyone's life easier and you know it!