DMARC is an email authentication protocol designed to prevent spoofing and phishing attacks. It works by verifying that messages sent from your domain are actually from your domain, and then applying a policy to those messages. This helps to ensure that only legitimate messages are delivered to your recipients, and helps to protect your domain from being used for malicious purposes. It builds on the SPF and DKIM authentication mechanisms to provide an additional layer of protection for email senders and recipients. DMARC also provides a reporting function that can be used to monitor email abuse and identify potential problems.