If you lose the password to a mailing list, you can use the Terminal to set a new one. This requires System Administrator (root) privileges. Use this command in Terminal:
$sudo /usr/share/mailman/bin/change_pw --listname=mailman --password=newpassword
Note: Replace "newpassword"with the password you want to set for this list.
To see other password modification options for mailman, use this command:
/usr/share/mailman/bin/change_pw --help