What is DMARC?
The DMARC (Domain-based Message Authentication, Reporting and Conformance) specification combines the SPF and DKIM procedures. While SPF defines which server is authorized to send an email, and DKIM ensures that this email has been transmitted unchanged by the sender, DMARC specifies how the recipient should handle emails that do not meet the requirements defined in one or both cases.
DMARC uses, like SPF and DKIM, a TXT record in the domain’s DNS settings, where it is configured to what extent SPF and DKIM influence the evaluation of an email’s legitimacy and what should happen in case of verification errors. Additionally, DMARC offers the possibility to receive email reports on such verification errors.
You can find all details regarding DMARC at dmarc.org.