DMARC

DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication protocol that builds on SPF and DKIM to provide comprehensive protection against email spoofing and phishing attacks. DMARC allows domain owners to specify how receiving mail servers should handle emails that fail authentication checks, providing both security and valuable feedback about email authentication performance. For cold email marketers, implementing DMARC is increasingly important as major email providers require it for optimal deliverability.

DMARC works by checking that emails claiming to be from your domain actually pass either SPF or DKIM authentication, and that the authenticated domain aligns with the ‘From’ address visible to recipients. DMARC policies can be set to ’none’ (monitoring only), ‘quarantine’ (send suspicious emails to spam), or ‘reject’ (block suspicious emails entirely). The protocol also provides detailed reports showing authentication results, sources of legitimate and illegitimate email, and potential security threats, giving domain owners unprecedented visibility into how their domain is being used for email communication.

Implementing DMARC requires careful planning and gradual deployment to avoid blocking legitimate emails. Start by publishing a DMARC record with a ’none’ policy to collect data about your email authentication performance without affecting delivery. Analyze DMARC reports to identify all legitimate email sources and ensure they’re properly configured with SPF and DKIM. Gradually increase policy enforcement from ’none’ to ‘quarantine’ to ‘reject’ as your authentication setup improves. Configure report analysis tools or services to help interpret DMARC data and identify issues. Monitor the impact on deliverability and recipient complaints as you tighten DMARC policies. Remember that DMARC is particularly important for cold email because it helps establish your legitimacy as a sender and protects your domain from being spoofed by malicious actors, which could damage your sender reputation even when you’re following best practices.