Ranked in these QuestionsQuestion Ranking
Pro Easy to use
Most Linux distributions that come with Exim, come with sane Exim default configurations. Changing default values and slightly adjusting configuration is relatively easy. On the other hand, building a completely new Exim configuration file from scratch might not.
Pro Sendmail compatible
Exim is a drop-in replacement for Sendmail.
Pro Good documentation
Exim provides thorough documentation with great examples.