DMARC (Domain-based Message Authentication, Reporting and Conformance) is an email authentication protocol that builds on SPF and DKIM to help prevent email spoofing and phishing. Here are the key points about DMARC:
- Purpose: DMARC allows domain owners to specify how to handle emails that fail SPF and DKIM authentication checks.
- How it works:
- Uses SPF and DKIM to authenticate emails
- Checks if the From address domain aligns with the authenticated domain
- Specifies a policy for handling failed messages (none, quarantine, or reject)
- Provides a mechanism for reporting results back to the domain owner
- Key components:
- Authentication: Leverages SPF and DKIM checks
- Alignment: Ensures the From address matches the authenticated domain
- Policy: Instructs receivers on how to handle failed messages
- Reporting: Allows domain owners to receive feedback on authentication results
- Benefits:
- Protects against email spoofing and phishing
- Improves email deliverability for legitimate senders
- Provides visibility into email authentication results
- Helps maintain domain reputation
- Implementation:
- Publish a DMARC record in DNS as a TXT record
- Start with a monitoring policy before enforcing strict rules
- Gradually increase enforcement as you analyze results
- Best practices:
- Begin with “p=none” policy to monitor without affecting delivery
- Review reports and adjust SPF/DKIM as needed
- Incrementally increase to “p=quarantine” and “p=reject” policies
- Use subdomains to test stricter policies
DMARC is an important tool for securing email communications and protecting domains from unauthorized use in phishing and spoofing attacks.