What is DMARC RFC & What is Its Role in Email Authentication

DMARC RFC (RFC 7489) is a technical standard defining how the protocol functions to authenticate email. This post explores its key concepts, integration with other protocols, and best practices for implementation to strengthen email security.

What is DMARC RFC?

DMARC RFC 7489, published in 2015 by the Internet Engineering Task Force (IETF), defines DMARC as a protocol designed to give domain owners control over how unauthenticated emails are handled. DMARC builds on two existing protocols – Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) – to provide a more robust authentication mechanism for email.

Through DMARC, organizations can publish policies instructing receiving mail servers on what to do with email messages that fail authentication. By specifying an enforcement policy, domain owners gain protection against email-based attacks and reduce the chance of their domains being exploited in spoofing attempts. DMARC also includes a reporting component, allowing domain owners to receive feedback on authentication results and evaluate the effectiveness of their DMARC policies.

Key Concepts 

DMARC RFC is built on a few key concepts:

• Policy: A DMARC policy defines the action a receiving mail server should take when an email fails authentication. The policies are expressed as p=none, p=quarantine, and p=reject.
  • p=none: This is the monitoring mode where no action is taken on unauthenticated emails.
  • p=quarantine: The email is marked as spam if it fails authentication.
  • p=reject: The email is outright rejected by the receiving server if it fails authentication. This is the most restrictive and secure setting.
• Alignment: DMARC uses alignment to match the domain in the From header with the domains used in SPF and DKIM. Alignment ensures that both SPF and DKIM are tied to the sender’s domain, making it harder for attackers to spoof emails.
  • SPF Alignment: This requires that the domain in the “Return-Path” matches the domain in the “From” header.
  • DKIM Alignment: This requires that the domain specified in the DKIM signature (DKIM d=) aligns with the domain in the “From” header.
• Reporting Mechanisms: DMARC includes reporting options that allow domain owners to receive aggregate reports and forensic reports on authentication performance.
  • Aggregate Reports (RUA): These reports provide data on email messages that pass or fail DMARC validation. These reports include information such as the source IP addresses, results of SPF and DKIM authentication, and the final disposition of the email.
  • Forensic Reports (RUF): These reports provide more detailed information on individual messages that failed DMARC checks, aiding in troubleshooting and fine-tuning.

Together, these components empower domain owners to monitor and enforce how their domains are used in email communication.

How DMARC RFC Integrates with SPF and DKIM

DMARC works in tandem with SPF and DKIM to validate emails, and its RFC provides a clear outline for how each protocol contributes to authentication:

• SPF: SPF validates that the IP address sending the email is authorized to do so by the domain in the email’s “Return-Path.” However, SPF has limitations because it does not verify the visible “From” address, which attackers often manipulate. This is where DMARC’s alignment feature becomes valuable.
• DKIM: DKIM verifies that an email’s content has not been altered in transit by adding a cryptographic signature. Like SPF, DKIM does not verify the visible “From” domain, but DMARC enforces alignment with this domain to strengthen authentication.

If either SPF or DKIM is aligned with the “From” domain, DMARC considers the message authenticated. This dual validation layer improves overall email security and helps prevent domain spoofing.

Why Businesses Should Implement DMARC 

As email threats become more sophisticated, implementing DMARC has become critical in securing business communications because it provides:

• Protection Against Phishing and Spoofing: With a p=reject policy, businesses can significantly reduce the risk of their domain being used for phishing attacks.
• Enhanced Brand Trust: DMARC implementation improves email deliverability and brand reputation, as legitimate messages from authenticated sources are more likely to reach recipients’ inboxes.
• Valuable Reporting: DMARC reports allow domain owners to analyze authentication results and monitor unauthorized activity. This information can help organizations identify and block malicious senders.

Conclusion

DMARC RFC offers a robust framework for protecting domains against email abuse by providing clear standards for DMARC implementation. By following the guidelines outlined in the DMARC RFC, businesses can take control of their email security, safeguarding their domain against phishing and other attacks. 

Contact us to find out how we can protect your domain with our DMARC solutions.