Email fraud, phishing and spoofing are serious threats to businesses and users. DMARC (Domain-based Message Authentication, Reporting, and Conformance) helps protect email domains against abuse. In this article you will learn what DMARC is, how it works and how to implement it.

What is DMARC?

DMARC is an email authentication protocol that helps protect your emails against spoofing and phishing. It works together with SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) to check whether an email really comes from an authorized sender.

With DMARC you can:

  • Prevent cybercriminals from abusing your domain for phishing.
  • Gain control over emails sent on behalf of your domain.
  • Get insight into email traffic through DMARC reports.

How does DMARC work?

DMARC builds on SPF and DKIM:

  • SPF checks whether the sender of the email is authorized to send on behalf of the domain.
  • DKIM adds a digital signature to the email, which safeguards the integrity of the message.
  • DMARC combines these methods and adds a policy, so you can decide what happens to emails that don't meet the authentication requirements.

DMARC uses three policy types:

  1. none: Report only, without taking action.
  2. quarantine: Suspicious emails are placed in the spam folder.
  3. reject: Emails that fail authentication are rejected.

Why is DMARC essential?

DMARC helps fight:

  • Phishing: Cybercriminals often use forged emails to steal sensitive data.
  • Email spoofing: Malicious parties can pretend to be your organization.
  • Brand damage: Bad emails that appear to come from your domain can damage your reputation.

By setting up DMARC correctly, businesses can secure their email domains and achieve better email deliverability.

Implementing DMARC: step by step

  1. Set up SPF and DKIM
    Make sure your domain has SPF and DKIM records.

  2. Create a DMARC record
    Add a TXT record to your DNS settings with the following basic configuration:

    v=DMARC1; p=none; rua=mailto:report@yourdomain.com; ruf=mailto:forensic@yourdomain.com; pct=100;

  3. Set the DMARC policy

    • Start with p=none to only collect reports.
    • Move to p=quarantine once you are sure SPF and DKIM work properly.
    • Eventually use p=reject to block all fraudulent emails.

  4. Analyze DMARC reports
    Check the reports to see which emails fail SPF and DKIM, and adjust your settings where needed.

Examples of DMARC records

Correctly configured DMARC record:

v=DMARC1; p=reject; rua=mailto:dmarc-report@yourdomain.com; ruf=mailto:dmarc-forensic@yourdomain.com; pct=100; sp=reject;

Common mistake:

v=DMARC1; p=none; rua=mailto:dmarc-report@yourdomain.com

❌ Mistake: A ruf value for forensic reporting is missing, and no action is taken against unauthorized emails.

Best practices & common mistakes

✅ Start with a low threshold (p=none) and raise it gradually.
✅ Check your SPF and DKIM settings before you implement DMARC.
✅ Use an external DMARC analysis tool for detailed reports.
❌ Don't use overly strict rules without testing.
❌ Don't forget to analyze your reports regularly and adjust your settings.

Monitoring and optimization

Once DMARC is active, you can keep improving it by:

  • Analyzing reports and adding domains to your SPF record where needed.
  • Moving to p=reject as soon as you are sure all authorized emails are delivered correctly.
  • Testing regularly with DMARC testing tools.

With DMARC you not only increase the security of your emails, you also build trust with your customers and partners. Don't wait any longer and implement DMARC today!

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