SASLAuthentication.registerSASLMechanism("DIGEST-MD5",SASLDigestMD5Mechanism.class);SASLAuthentication.supportSASLMechanism("DIGEST-MD5");You don't need to do that, DIGEST-MD5 is enabled per default in Smack.
Enable Smack debug by setting SmackConfiguration.DEBUG to true and show us the communication between Smack and the Server.