As of today many XMPP services will begin refusing unencrypted connections. Peter Saint-Andre laid out a plan for strengthening the security of the network last year. The Prosody Team has signed a manifesto to date signed by over 70 service operators and software developers. Today’s change only ensures encryption (enough to beat passive capturing of traffic), it does not require you to have a valid certificate issued by a certificate authority. Some current initiatives include DNSSEC, Monkeysphere, and some folks prefer to trust nothing less than hand-verified fingerprints.”]
Source: https://blog.prosody.im/mandatory-encryption-on-xmpp-starts-today/