I want my users to stop accessing user accounts like IMAP, SMTP and POP without SSL. I can easily disable non-SSL access, but then everything would break. Is there a way to automatically redirect them? With HTTP it's easy, but with this...? I mean, if the client is configured without SSL, it's not just going to accept SSL, so a simple port redirect isn't going to cut it.
There's no way (that I know of) to redirect these protocols like it's possible with HTTP.
However, you could set up the TLS enabled servers to the standard TLS ports and also add support for STARTSSL/STARTTLS in non-TLS ports. With STARTTLS many clients might already use secured channel to communicate.
Then little by little start migrate your users to TLS enabled services and announce date when non-TLS services stop working.