Like I did with NetBSD, this is how to build an almost complete Mail Server with OpenBSD.
We’re gonna use a Dovecot IMAP server and a Postfix SMTP server. Postfix will use Dovecot as a SASL service. Both will use LDAP to identify valid users and e-mail aliases. Mail sanitization will be provided by RBL, from Postfix, and by the
spamd shipped with OpenBSD.