DMARC

DMARC, which stands for “Domain-based Message Authentication, Reporting & Conformance,” is an email protocol that uses SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) to determine the authenticity of an email message. DMARC helps prevent spammers from using fake email addresses (often from well-known domains) in the “From” field, a tactic known as email spoofing.

How DMARC Works:

  1. Email Sending: When an email is sent, the sending mail server adds DKIM signatures to the email headers and the domain’s SPF record is published in its DNS.
  2. Email Receiving: The receiving mail server checks the incoming email for SPF and DKIM records.
  3. DMARC Verification: The receiving mail server then checks the DMARC record for the sending domain via DNS. This record tells the receiving server how to handle emails that fail SPF and DKIM checks.
  4. Policy Application: If the email passes the DMARC checks, it’s delivered. If it fails, the receiving server takes action based on the DMARC policy set by the domain owner (e.g., reject the email, quarantine it, or do nothing).
  5. Reporting: The receiving server sends reports about email authentication status back to the domain owner. This helps domain owners understand who is sending email on their behalf and if any fraudulent activity is taking place.

Benefits of DMARC:

  1. Increased Email Security: DMARC significantly reduces the potential for email-based attacks like phishing and spoofing.
  2. Enhanced Trust: When recipients see that an email is DMARC-compliant, they can trust that the email genuinely comes from the stated domain.
  3. Improved Deliverability: With DMARC, emails are more likely to land in the recipient’s inbox rather than the spam or junk folder.
  4. Visibility: Domain owners gain insight into who is sending emails on their behalf, which helps in identifying legitimate senders and malicious actors.

DMARC Policies:

DMARC allows domain owners to specify policies that dictate how receiving servers should handle emails that fail DMARC checks:

  • None (p=none)No specific action is taken on failed emails, but reports are still generated and sent to the domain owner.
  • Quarantine (p=quarantine)Emails that fail DMARC checks are moved to the spam or junk folder.
  • Reject (p=reject)Emails that fail DMARC checks are rejected and not delivered to the recipient.

In conclusion, DMARC is an essential tool in the fight against email spoofing and phishing. By combining the powers of SPF and DKIM and adding a layer of accountability, DMARC provides a way for domain owners to protect their reputation, enhance trust in their emails, and improve email deliverability. Implementing DMARC is a best practice for organizations looking to secure their email communication.

Key terms in plain language

Open a term for a concise explanation of language used on this page.

Cybersecurity

The practices and controls used to protect identities, devices, networks, applications, and data from unauthorized access, disruption, or manipulation.

Zero Trust

A security model that does not automatically trust a user or device because of its location. Access is continuously verified and limited to what is necessary.

SASE

Secure Access Service Edge combines networking and security capabilities in a cloud-delivered architecture so users and locations can receive consistent policy wherever they connect.

Identity and Access Management (IAM)

The systems and policies that determine who a user is, what resources they may access, and how that access is authenticated and reviewed.

Multi-Factor Authentication (MFA)

A login control requiring more than one form of verification, such as a password plus an authenticator app, security key, or biometric factor.

MDR / XDR

Security services and tools that monitor activity, investigate suspicious behavior, and help contain threats. MDR is managed detection and response; XDR correlates signals across multiple security layers.