Need help to improve mail server security

==== Required information ====
- iRedMail version: 0.8.6
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Linux/BSD distribution name and version: cento 6
- Related log if you're reporting an issue:
====

Hi zhang,

Can you guide me how to disable PLAIN and AUTH Login on port 25 and  i  also need to enable SMTP SSL.

Thanks