Review mailman configuration on OpenSUSE 12.x
http://www.howtoforge.com/forums/showpost.php?p=304305&postcount=3 http://www.howtoforge.com/forums/showpost.php?p=304306&postcount=4 http://www.howtoforge.com/forums/showpost.php?p=304321&postcount=5
The patches in the above-mentioned forum posts are working as expected, but until now one has to make sure manually that there's no mailing list and mailbox/mail-alias with the same name.