Postfix has been used on my mail servers for a number of years. My other servers only need minimal email to send out periodic reports, so Sendmail from the base system is adequate, easily started from
/etc/rc.conf and works out of the box (until recently).
After updating FreeBSD to 10.1-RELEASE-p12 a couple of days ago, to address a security advisory relating to OpenSSL, Sendmail now refuses to work. Long story short, I decided to take this opportunity to replace Sendmail with a submit-only PostFix installation.