Topicbox can absolutely function as a replacement for your listserve or mailing list, whether it's hosted on a Mailman or majordomo install, or you use a listserve service like Google Groups or Yahoo Groups.
We think Topicbox is better than a listserve for organizations with more than one listserve (what we call a group.) Most listserves are centered around the idea of the group, and Topicbox is centered around the idea of the organization.
Topicbox makes it easier for administrators to:
Trusted members can:
All members should find it easier to: