I don't want ejabberd to allow incoming or outgoing connections to other servers. How can I disable S2S connections?
Jabber servers use a dialback method to establish a connection between them. So, if you configure ejabberd to not listen for incoming S2S messages, ejabberd will not be able to connect to other Jabber servers.
To disable incoming messages, you must disable ejabberd_s2s_in from the listening sockets in ejabberd configuration.