DMARC (Domain-based Message Authentication, Reporting & Conformance) significantly impacts email deliverability by providing a framework for authenticating email and protecting domains from unauthorized use such as spoofing and phishing. It relies on SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) and allows domain owners to specify how recipient mail systems should handle messages that fail authentication. While DMARC is not directly a deliverability protocol, successful implementation can improve inbox placement, protect brand reputation, and increase ROI for email marketing efforts. Key benefits include enhanced visibility into email streams, protection against phishing attacks, and improved brand reputation. However, DMARC implementation can be challenging, requiring a careful understanding of reporting, proper authentication of all legitimate sending sources, and a phased deployment approach. A poorly configured DMARC policy, especially a 'reject' policy, can inadvertently block legitimate email. DMARC reporting provides valuable insights into an organization's email ecosystem, enabling identification and resolution of deliverability issues.