Configure POP/IMAP to use SSL/TLS for secure communication

This needs to be done after creating the certificate authority

#yum install dovecot -y

Edit /etc/dovecot.conf to allow on the protocols you require by changing the protocols value

Edit /etc/pki/dovecot/dovecot-openssl.cnf with the relevant information

Delete the old certificates

#rm /etc/pki/dovecot/private/dovecot.pem

#rm /etc/pki/dovecot/certs/dovecot.pem

Run the mkcert script
#/usr/share/doc/dovecot-1.0.7/examples/mkcert.sh

Restart dovecot
#service dovecot restart

Open the required ports on the firewall

ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:imaps
ACCEPT     udp  --  anywhere             anywhere            state NEW udp dpt:imaps
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:pop3s
ACCEPT     udp  --  anywhere             anywhere            state NEW udp dpt:pop3s

You can test this using mutt, copy the ca certificate to the .mutt directory in the users home directory and run mutt

#mutt -f imaps://user@server

Check the maillog of the server 

Sep  4 13:32:40 auth1 sendmail[6037]: q84KWdRd006036: to=<adam@auth1.example.com>, ctladdr=<root@auth1.example.com> (0/0), delay=00:00:01, xdelay=00:00:00, mailer=local, pri=30529, dsn=2.0.0, stat=Sent

Sep  4 13:34:02 auth1 dovecot: imap-login: Login: user=<user>, method=PLAIN, rip=::ffff:172.16.118.135, lip=::ffff: TLS