This affected me on 14.04, too. Luckily, after running this command, both existing lists and new lists had the right permissions:
sudo chgrp -R list /var/lib/mailman/archives/private -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/543148 Title: Private Archive Permissions Are Incorrect To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/mailman/+bug/543148/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs