Set Up OpenDMARC with Postfix on CentOS/RHEL to Block Email Spoofing

In previous articles, we discussed several effective tips to block email spam. This tutorial will be showing you how to set up OpenDMARC with Postfix SMTP server on CentOS/RHEL to block email spoofing and spam. OpenDMARC is an open source DMARC email policy filter for MTAs (Message Transport Agent, aka SMTP server).

What is DMARC

DMARC (Domain-based Message Authentication, Reporting and Conformance) is an Internet standard (RFC 7489) that allows domain owners to prevent their domain names from being used by email spoofers. Before DMARC is invented, it is very easy for bad actors to use other people’s domain name in the From address.

If a domain owner created DMARC DNS record for his/her domain name and a receiving email server implemented DMARC verification, then bad actors need to pass SPF alignment or DKIM alignment in order to pass DMARC verification. If DMARC check fails, the spoofed email could be rejected. Never to be seen by end users. It’s difficult for the bad actor to pass SPF or DKIM, unless the domain owner’s email server is compromised.

Read full tutorial here: https://www.linuxbabe.com/mail-server/block-email-spam-postfix