We use minger across physical locations to relay emails between servers, for the same domain. So, if the account "Ray" is on server 2, but mail comes in on server 1 first, it is relayed to server 2 (if the account exists). That allows me to not have the Ray account on server 1. A similar "concept" would be nice across servers, for xmpp. So for now, if I tie-in my xmpp client on server 2, I cannot "see" or talk to the users on server 1. Maybe Minger is not the correct feature to point out, but the "spirit" of its functionality is what I was thinking about.