Sendmail

Sendmail: the default SMTP and local mail delivery service on FreeBSD and most other unixlike systems. It is ubiquitous because it is very literally the original mail program; however in the opinion of many administrators it is an evil festering mess worth of Microsoft and should be replaced at first opportunity, due to a long history of overcomplexities, security holes, and general cruftiness.

The freebsdwiki.net maintainers use and recommend qmail as a Sendmail alternative, and HIGHLY recommend that you install qmail (or failing that, just about anything else) in place of Sendmail if you are planning to run an actual production mailserver.