@evan @elipariser @vanderwal sorry for the necro, but regarding Evan's Triangle-- what if, for wide distribution, you use the tape tree concept? That is, the sending server distributes to a much smaller number of intermediary servers, each of which sends to a fraction of the recipient list? It would be non-trivial-- for one thing, the intermediaries would have to know which recipients they're responsible for-- but I'm not convinced it's not possible. Not much load on any one server.