DMARC (Domain-based Message Authentication, Reporting, and Conformance) is an email authentication protocol that helps protect organizations and individuals from email spoofing, phishing, and impersonation attacks. It works by allowing domain owners to specify how email servers should handle messages that appear to come from their domain but fail authentication checks. DMARC builds on existing SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) protocols, providing a way to monitor, reject, or quarantine suspicious emails. This helps ensure that only legitimate emails are delivered, improving trust and reducing the risk of cyberattacks.