DMARC (Domain-based Message Authentication, Reporting, and Conformance) is a DNS record that can be added for a site to help prevent email spoofing from malicious parties. It is more frequently being adopted as a mailing requirement by email providers like Google and can affect deliverability rates if not in place.
We recommend reviewing the documentation from both your email delivery platform as well as common recipient platforms like Gmail and Outlook to determine the appropriate DMARC records and how to implement this into your site's DNS