I'm beating my head over this, maybe someone else can shed some light.
Virtualmin (Dovecot 2.2.10 + Postfix 2.10.1)
If I run the email without ssl I get:
The IMAP server did not accept the username and/or password: A0001 NO [AUTHENTICATIONFAILED] Authentication failed
If I run it with say the port at the end
An error occured while sending or receiving mail. Could not read from the stream. It was probably terminated by the host.
I know the username and password work, I used roundcube to check. However, I did find that my system doesn't accept 993 or 995. Thunderbird won't connect. My mail log has shown:
Login: user=<user.domain>, method=PLAIN, rip=18.104.22.168, lip=22.214.171.124, mpid=30168, secure, session=<HZzHUjRqFQBot0T6>
if you need any other info, lemme know