DMARC
An email policy that tells receiving servers what to do when SPF or DKIM authentication fails.
Why It Matters
DMARC prevents domain spoofing and phishing attacks while giving you visibility into who is sending email using your domain.
How It Works
You publish a DMARC policy in DNS specifying whether to monitor, quarantine, or reject emails that fail SPF and DKIM checks. Receiving servers enforce this policy and send aggregate reports back to you.
Real-World Example
A company sets DMARC to p=quarantine, causing spoofed emails using their domain to land in spam instead of inboxes.
Common Mistakes
Jumping straight to p=reject without monitoring first
Not reviewing DMARC aggregate reports regularly
Related Terms
A DNS record that specifies which mail servers are authorized to send email on behalf of your domain.
An email authentication method that adds a cryptographic signature to verify messages haven't been altered in transit.
A score assigned to your sending domain and IP by email providers that determines inbox placement.
DMARC FAQs
What DMARC policy should I start with?
Start with p=none to monitor authentication results, then gradually move to p=quarantine and finally p=reject.
Is DMARC required for bulk senders?
Yes, Google and Yahoo require DMARC for senders exceeding 5,000 emails per day as of February 2024.
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