Server is 'localhost'. Now what?

Ok, so, the only server setup that work is with 'localhost' as hostname. My goal is to setup my mac with a jabber server and msn transport so that I don't need to rely on external server. But now, I can't log to other servers or anything. I can log to my server with name like 'swan@localhost' but what if someone from the outside want to log to my server? Did I missed something? 'Cause I want to log with my dynamic hostname (swanturcotte.ath.cx) instead of 'localhost', but , as I said, the only setup that work so far is with 'localhost'...

I hope I am clear...