I have a web server that also is my mail server - running dovecot and exim4. I currently have 5 open ports that have to do with serving mail, it seems very excessive to me. Its a dedicated box, I have root access - and most importantly I have control over everyone who receives mail from the box - so I can tell them to configure their mail clients any which way I prefer.
25/tcp open smtp 110/tcp open pop3 143/tcp open imap 993/tcp open imaps 995/tcp open pop3s
What is the most secure way to serve mail?
Can I close ports 110 and 143, and just tell everyone to set their clients to receive on 993 and 995?
Is the mail served out of 993/995 fully encrypted, ie: not able to be eaves-dropped?