[Dovecot] Force SSL authentication per user basis

Hi,

I'm searching a way to force encrypted connections for POP3/IMAP on a per user basis.

To not break clients which still connect in plaintext (there are still many of it) I must implement a mechanism to force encrypted connections on a per user basis.

The users and passwords are stored in a mysql database. So there would be no problem to expand the database with a column like "ssl_tls" -> yes/no.

The problem now: how can I get dovecot to process this field in the right way? I searched the list and googled about such a way, but I can't find any solution.

My Dovecot version is 2.2.12.

Many thanks and regards Urban Loesch