iRedMail
// Document IndexWARNING: With postscreen service enabled, your users must use port 587 to send email, port 25 will be used by postscreen service instead of normal smtp service.
iRedMail ships a script to enable postscreen. You can enable it with steps below:
enable_postscreen.sh from iRedMail source code
repository# bash enable_postscreen.sh
That's all.
Important notes:
/etc/postfix/main.cf and /etc/postfix/master.cf first,
if postscreen doesn't work, you can restore these 2 files./etc/postfix/main.cf (Linux/OpenBSD) or /usr/local/etc/postfix/main.cf
(FreeBSD) to check the DNSBL servers it enabled, you're free to remove some
of them (or add new ones) if you want.If you don't want to use postscreen service, you can enable DNSBL service instead, it helps a lot too, but less effective than postscreen service.