Participating in a mailing list

"NNTP is the Usenet protocol, your email list does not use it. But you have some options.

Emacs Gnus is a Usenet news reader that can sort mail into groups, and then thread them like newsgroups.

Gmane serves mailing lists through NNTP. You can check to see if your list is included, or ask it to be included if it is not."

Use a gmail account - threaded emails are perfect for mailing lists. And, use labels to group messages from each list. Works a treat.

I know this does not directly answer your question, but one option is to encourage groups that use mailing lists to move to a forum/bulletin board format.