Binary package “postfix” in ubuntu maverick

High-performance mail transport agent

 Postfix is Wietse Venema's mail transport agent that started life as an
  alternative to the widely-used Sendmail program. Postfix attempts to
  be fast, easy to administer, and secure, while at the same time being
  sendmail compatible enough to not upset existing users. Thus, the outside
  has a sendmail-ish flavor, but the inside is completely different.