Postfix

Postfix is a fast, easy-to-administer, and secure open source mail transfer agent (MTA).

Postfix is an open source mail transfer agent (MTA), a computer program for the routing and delivery of email, that is intended as a fast, easy-to-administer, and secure alternative to the widely-used sendmail. Formerly known as VMailer and IBM Secure Mailer, it was originally written by Wietse Venema during a stay at the IBM Thomas J. Watson Research Center, and continues to be actively developed today.