In previous tutorials, we discussed how to set up a mail server from scratch on Linux (Ubuntu version, CentOS/RHEL version). This tutorial is going to show you how to enable and configure Postscreen in Postfix SMTP server. Postscreen is an SMTP filter that blocks spambots (or zombie machines) away from the real Postfix smtpd daemon, so Postfix does not feel overloaded and can process legitimate emails more efficiently.
Note: If you are using iRedMail or Modoboa, then Postscreen is enabled by default on your server. Still, you will learn something new.
Read full tutorial here: https://www.linuxbabe.com/mail-server/configure-postscreen-in-postfix-to-block-spambots
