Open Cobalt contains an XMPP/Jabber client that is used for both normal text messaging and for ad-hoc world rendezvous. Unfortunately this client currently has some limitations in it's understanding of XMPP and may require some custom setup of the server. Most specifically it uses the legacy SSL port instead of the STARTTLS mechanism for security. The client also doesn't currently use DNS SRV records in the server lookup process. This means that the domain part of the user id needs to be the same as the domain name of the server.
XMPP servers that have worked successfully are: