-# SMTP (allowing for STARTTLS); necessary for mail server to mail server banter
--A INPUT -p tcp --dport 25 -j ACCEPT
-# SMTPS, for mail server to mail user agent communication
--A INPUT -p tcp --dport 465 -j ACCEPT
-# IMAPS
--A INPUT -p tcp --dport 993 -j ACCEPT
-# tolerate any inbound connections requested by our server, no matter the port
--A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT