Does Mailman usually have a default mailman@yourdomain list? We recently set up a new instance of Mailman on our new server and it seems to have one by default, but all it gets is spam from other websites' mailman@ lists, and I'm not sure where it came from. Working on Debian Lenny.
Yes, it's a default list setup for all of the monthly password spam^Wreminders that get sent out, and some other (rare) administrative e-mails. It's been created by default on all new installs for at least the last couple of years.