I'm open to correction, but I believe it's essentially a bunch of email lists. You can post to rec.games.roguelike.angband, your message will go to a server somewhere (theoretically, to every Usenet provider), and people who want to discuss, or read discussion of, Angband, can ask that server for the set of messages associated with rec.games.roguelike.angband.
So email, if you sent mail to topics rather than to recipients.
So email, if you sent mail to topics rather than to recipients.