OpenSMTPD Is The Mail Server For The Future

Summary

OpenBSD 7.9 will leave the exim package behind, and exim users will need to find a replacement. OpenSMTPD (smtpd) is in the base system. When OpenSMTPD was first introduced in the OpenBSD base system in OpenBSD 4.6 in October 2009, I had already been running a mail service for some years. At the time I still found it convenient to keep using exim as the real mail server, protected by OpenBSD spamd in the incoming signal path and with a combination of spamassassin and clamav for content filtering. It seemed quite tempting to me to play around with at the new smtpd at the time, but the initial version of the new mail server was not yet considered quite ready for prime time. Note: This piece is also available without trackers but classic formatting only here. The pace of development was quite hectic in the early years, and by the time smtpd replaced the classic sendmail as the default mail server in OpenBSD with the November 2014 OpenBSD 5.6 release, I had just completed the third edition of The Book of PF and I was interested, but the writing had been quite a drain on my energy. And of course, the mail server setups I had running for myself and friends I thought of as complex enough that moving to something else would require quite some preparation and testing. So I would leave looking into the new mail server software properly for another day, soon to come, I was sure. An Old Setup, Maintained With Much Love and Care There are some hints of what that setup did (and still does) in the 2012 piece In The Name Of Sane Email: Setting Up OpenBSD's spamd(8) With Secondary MXes In Play - A Full Recipe (also tracked, prettified), but the main features are: Two (originally three) separate sites, each with their own domains, where the other site(s) provide secondary MX duty for the other(s), each with a spamd-instrumented OpenBSD machine as the Internet-facing part of the mail setup The OpenBSD machines perform spamd greylisting and greytrapping, but also provide content filter...