I have hacked Petidomo to support what I call split lists. The key difference between a split list and other formats is that in a plit list the concepts of subscription or membership is seperate from that if posting authority. This would be a split moderated list as above. So far it works wonderfully. Majordomo works this way.
Most lists have posts restricted to members.
I am sure that Lyris operates similarly, and probably the other big ones such as Listserv. Your E - mail List Review of The Day. The E - mail Discussion List Exclusively for List Moderators. Your Source For Free Targeted New E-mail List Announcements. The Newbie's Guide to E-mail List Terminology.