I know this problem very well, but I think the issue is mainly due to bad bounce processing (at least I hope linux users are not so stupid to complain about a ml they subscribed). At the moment I don't host public mailing lists anymore but I had the very same problems when I did. Fortunately I own a /28 subnet and I will surely use a separate ip next time I will need to host a public ml.
Thanks for doing this, Niccolò -- List info: http://lists.roundcube.net/users/ BT/8f4f07cd
