Ranked in these QuestionsQuestion Ranking
Pro Excellent security
Qmail was built ground up with security in mind.
Qmail parallelizes mail delivery to increase speed.
Pro Sendmail compatible
Qmail is a drop-in replacement for Sendmail.
Pro Easy to maintain
Configuration of Qmail is sane and straightforward.
The original author of Qmail stopped maintaining it in 1998. It was released to public domain in November 2007.