Security

What Is DMARC and Why Should You Care?

In today’s threat-filled digital world, email remains one of the most abused communication channels for phishing and spoofing. That's where DMARC (Domain-based Message Authentication, Reporting, and Conformance) steps in. DMARC is a powerful DNS-based protocol that helps domain owners protect their email reputation by verifying that emails really come from their domain—and giving them control over what happens when spoofing attempts occur.

What DMARC Does:

  • Verifies email sources: Ensures messages claiming to be from your domain are properly authenticated using SPF and DKIM.
  • Provides reports: Gives detailed feedback from receivers about how your domain is used in email traffic.
  • Sets policies: You can tell mail servers how to handle unauthenticated messages—monitor, quarantine, or reject.

How to Enable DMARC in 5 Steps:

  1. Ensure SPF and DKIM Are Set Up
    • SPF: Add a TXT DNS record that defines which servers are allowed to send emails for your domain.
    • DKIM: Configure your email server to sign outgoing messages using a private key and publish the public key as a DNS record.
  2. Create Your DMARC Record
    • The DMARC record is a TXT record placed on _dmarc.yourdomain.com.
    • Example record (monitor-only):

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

  1. Publish the Record in DNS
      • Log into your DNS provider.
      • Add a new TXT record with the name _dmarc and the value from Step 2.
  1. Monitor Reports
      • Use services like Postmark, DMARC Analyzer, or open-source parsers to view your aggregate reports.
      • Watch for unauthorized use of your domain and mail flow failures.
  1. Enforce Policy Gradually
    • Start with p=none for monitoring.
    • Shift to p=quarantine then p=reject to block spoofing once you’re confident legitimate mail is flowing correctly

DMARC might seem like a “set it and forget it” kind of tool—but its true power lies in its reporting and policy tuning over time. Start simple, iterate wisely, and protect your brand’s inbox from becoming a spoofer's playground.

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