DMARC stands for Domain-Based Message Authentication, Reporting and Conformance.

The DMARC record has been designed as an additional security measure that helps to protect your email correspondence by preventing email spoofing. It does this by checking the headers of incoming email to determine whether the domain specified there is identical to the one defined in the SPF record.

The use of a DMARC record is an optional feature for experienced users, but typically it is not necessary.