I don't recall what the addresses were - but these servers would have a list of games and let you sign up for multiplayer games. You'd play your turn before it processed then on a specific schedule everyone's turn would process.
Those would be Mosehansen's servers, most probably. There was a thread in which Shrapnel people queried some people, including Mosehansen, about the costs of a running server. He and Gandalf also managed to solve few problems in having PbEM servers, so we might get one of those as well.