DMARC (Domain-based Message Authentication, Reporting and Conformance) is a control system and tells the receiving mail server whether to accept an e-mail message if SPF and/or DKIM failed.
To specify how the receiving mail server should handle failed (SPF and/or DKIM) checks, we can set the following parameters.
- p=none (let the receiving mail server decide)
- p=quarantine (set the e-mail as SPAM)
- p=reject (do NOT deliver the e-mail to the receiver)
To setup DMARC you have to create a subdomain with the following format
v=DMARC1; p=reject; rua=mailto:firstname.lastname@example.org;
With the rua= parameter the receiving mail server can notify the domain owner about abuse and problems.