DMARC (Domain-based Message Authentication, Reporting, and Conformance) is an email authentication protocol that builds on SPF and DKIM to give domain owners control over how receiving servers handle unauthenticated messages. It allows you to specify a policy of none (monitor only), quarantine (send to spam), or reject (block entirely) for emails that fail authentication checks.
For B2B sales teams, DMARC serves two critical functions. First, it protects your domain from being spoofed by unauthorized senders, which preserves your brand reputation and protects prospects from phishing attacks. Second, it improves your overall deliverability by signaling to email providers that you take authentication seriously and have full control over who sends email on your behalf.
DMARC also provides valuable reporting capabilities. When configured with a reporting address, you receive aggregate and forensic reports showing who is sending email using your domain, whether those emails pass or fail authentication, and how receiving servers are handling them. This visibility helps you identify unauthorized senders and troubleshoot authentication issues.
Key Points
- Builds on SPF and DKIM to enforce authentication policies
- Protects your domain from spoofing and phishing attacks
- Provides reports on email authentication results across all senders
How It Works
You publish a DMARC record in your DNS that specifies your authentication policy and reporting preferences. When a receiving server gets an email from your domain, it checks SPF and DKIM results against your DMARC policy. If neither passes and your policy is set to reject, the email is blocked. Reports are sent to the address specified in your DMARC record.
Best Practices
- Start with a DMARC policy of "none" to monitor results before enforcing
- Gradually move to "quarantine" and then "reject" as you confirm all legitimate senders pass authentication
- Review DMARC reports regularly to detect unauthorized use of your domain