My xmpp server requires SSL connections. In both Adium and Pidgin (libpurple) you must enable "force old style ssl" to successfully connect to our server.

The following StackOverflow entry discusses using SSL with Smack:
http://stackoverflow.com/questions/545082/how-to-create-an-ssl-connection-using-the-smack-xmpp-library

http://svn.igniterealtime.org/svn/repos/spark/trunk/src/java/org/jivesoftware/spark/util/DummySSLSocketFactory.java