Domain-based Message Authentication, Reporting, and Conformance (DMARC) is an email authentication protocol designed to protect domains from email spoofing, thereby improving email deliverability and sender reputation. By working alongside SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail), DMARC enables mail servers to verify the authenticity of incoming emails, guiding them on actions to take if authentication fails. The implementation process involves setting up DNS records and gradually adjusting DMARC policies from "none" to "quarantine" or "reject" to enhance email security, with SendGrid providing tools and guidance for this setup. Monitoring and reporting are crucial components of DMARC to identify unauthorized email activities and ensure legitimate emails pass through, with the option to use additional services like Valimail's DMARC Monitor for streamlined oversight. Transitioning to stricter DMARC policies is essential for incorporating Brand Indicators for Message Identification (BIMI), which visually enhances brand recognition in email communications.