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DMARC Checker

Domain-based Message Authentication, Reporting, and Conformance (DMARC) is an email authentication protocol.

RFC: RFC 7489
DEPENDENCIES: SPF, DKIM
POLICY: none, quarantine, reject

What is DMARC Checker?

DMARC uses SPF and DKIM to determine the authenticity of an email message. It allows domain owners to specify how receivers should handle emails that fail authentication.

How it Works

A DMARC policy is published in DNS as a TXT record. When an email is received, the receiver checks the SPF and DKIM status. If they fail, the receiver follows the action specified in the DMARC policy (p=none, p=quarantine, or p=reject).

Key Use Cases

Preventing domain spoofing and phishing attacks.

Improving email deliverability by proving identity.

Gaining visibility into who is sending email on behalf of your domain via DMARC reports.

Advanced Details

The "rua" tag in DMARC specifies where aggregate reports should be sent. These reports provide invaluable data on email authentication success and failure rates across the globe.

Cybersecurity Pros & Cons

Security Advantages
  • p=reject is the gold standard — it completely blocks spoofed emails from reaching recipients at compliant mail providers.
  • DMARC aggregate reports (RUA) provide a real-time intelligence feed of all entities sending mail claiming your domain.
  • Enables phased rollout (none → quarantine → reject) so organisations can harden without disrupting legitimate mail flows.
  • DMARC subdomain policy (sp=) extends protection to all subdomains, including parked and unused ones used for spoofing.
Security Limitations
  • p=none offers zero protection — it only monitors, yet many organisations remain at this policy indefinitely.
  • DMARC does not protect against cousin domain attacks (e.g., brand-corp.com vs. brand.com).
  • Misconfigured DMARC at p=reject can block legitimate bulk senders (CRM tools, helpdesks) that lack proper alignment.
  • DMARC reports contain sending IP data that could be used by attackers to map your email infrastructure.
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