spamd, the OpenBSD spam deferral daemon
Please add OpenBSD spamd (not to be mistaken with the SpamAssassin’s
daemon) to AlpineLinux.
As spamd requires pf, a port exists for iptables: https://github.com/martinh/spamd-iptables.
Actually, I’m not able to build it (issues with headers) but if you succeed it will be greatly appreciated as spamd is really efficient against spammers.
(from redmine: issue id 7699, created on 2017-08-17)