OpenSMTPD Frequently Asked Questions

OpenSMTPD (from here on referred to as smtpd) is a FREE implementation of the server-side SMTP protocol as defined by RFC 5321, with some additional standard extensions. It allows ordinary machines to exchange emails with other systems speaking the SMTP protocol. Started out of dissatisfaction with other implementations, smtpd(8) is a fairly complete SMTP implementation.

It is primarily developed by Gilles Chehade, Eric Faurot, Charles Longeau and Sunil Nimmagadda, with contributions from various OpenBSD hackers.

This set of documents is intended as a general introduction to smtpd(8) as used on OpenBSD. Even if it covers most of smtpd's features, it is only intended to be used as a supplement to the man pages, and not as a replacement for them. For a complete and in-depth view, please start by reading the smtpd(8), smtpd.conf(5) and smtpctl(8) man pages.

As with the rest of the FAQ, this set of documents is focused on users of the most current release of OpenBSD. As smtpd(8) is always growing and developing, there are changes and enhancements between the OpenBSD release version and the version in -current. There are also differences between the current version and earlier versions. The reader is advised to see the man pages for the version of OpenBSD they are currently working with.