Why use exim?

• Very flexible indeed - the Swiss Army Knife of MTAs. Especially good for:
  • E-mail policy control
  • E-mail routing control
  • Database-driven routing (e.g. mysql, LDAP)
• Clean design - major rework from exim3 to exim4
• Relatively easy to configure (considering its flexibility)
• Extremely comprehensive documentation
• Extremely good logging and debugging
• Good performance
  • Very solid and reliable
  • Widely used in large university and ISP environments (written in Cambridge University)
• The author, Philip Hazel, embraces his user community and welcomes feedback and contributions

Other modern MTAs you might wish to consider, especially if they are already in use at your organisation, include

• Postfix

Qmail is still widely used but quite old, and the author forbids the source to be distributed except his original unmodified version, so development is essentially frozen.

Sendmail is slowly trying to catch up but has a history of security problems, is still extremely hard to configure, and still not as flexible as Exim in terms of external database-driven routing.