Any forum software with tightly integrated listserv capabilities?

Any recommendations for some forum software that fully supports listserv-style email discussion list functionality? Specifically, a forum that users can access online in the typical fashion or choose to interact with it strictly through email (both sending and receiving messages) like a traditional email discussion list (like mailman or majordomo). Let me emphasize that a forum with simple outbound notification is not sufficient -- I need email responses from users to post back to the forum.

I'd accept a reasonably priced hosted solution as well if it has good support. Yahoo and Google groups feature email access, but I need more support than either of those free hosting providers offer (if something breaks I need to be able email or actually talk to someone to get it fixed).

+2 points for actively maintained open source software
+1 point for user account integration with some CMS
+1 point for NNTP support at the same time (probably a pipe dream :)
+X points for nice feature set (email bounce handling, moderation, good SEO, etc.)
+1 point for Windows hosting compatibility

So far the only option I've really found is the enterprise edition of ActiveForums for DotNetNuke. Surely there must be other packages like this out there though. Any suggestions?

From serverfault sbussinger

• you can try phpbb

  Ignacio Vazquez-Abrams : "listserv" is more than just "send email to a group of users".

  sbussinger : As Ignacio suggests, I'm looking for real email discussion support not just notifications (meaning for instance that you can add a message to a forum by replying to an email). If PHPBB supports this, it's certainly not obvious from their website.
  From Tumbleweed

• GroupServer is pretty nice, GPLed, and has a hosted option.

  You also have the option of running an nntp server and putting a web gateway in front of it. I've seen newsportal used, though FUDforum appears to be a more full-featured option.

  sbussinger : Thanks! GroupServer and FUDForum both look like possible options. Now I need to do some research and experimentation. GroupServer looks good but I'm nervous about the slowness of development (2 years from 1.0 alpha to 1.0 beta) and their own forums aren't very active. They have a free hosted option which is great, but the private hosted options are pretty expensive. FUDForum also looks good and has a lot of features. It has mailing list and NNTP interfaces but they aren't integrated into the product. Have you used either of these yourself?

  Tobu : Nope, at first I was just trying to remember the name of newsportal; they certainly are improvements.
  From Tobu