Postfix
From Funtoo Linux
Postfix is an advanced mail server, MTA (mail transport agent). Postfix attempts to be fast, easy to administer, and secure. The outside has a definite Sendmail-ish flavor, but the inside is completely different. Funtoo/Linux providing postfix as default MTA.
Installation
# emerge postfix
At this point emerge will try to replace any alternative MTA (if any) installed on your system. It is safe to proceed. WIP