Use the wayback machine https://web.archive.org/web/20160401100013/https://blog.corrupted.io/2014/06/09/OpenSMTPD-virtual-users-with-sqlite.html
Use the wayback machine https://web.archive.org/web/20160307204911/http://blog.admiral0.it/computing/mail-server-with-opensmtpd-dovecot-and-amavisdspamassassin