Skip to main content
Gmail

550 5.7.26 “not accepted due to domain's DMARC policy”

The domain in the From address publishes a DMARC policy that tells receivers to reject mail that fails authentication, and this message failed. The 451 version means Gmail couldn't finish the DNS lookups and will retry.

Codes: 550 5.7.26 or 451 4.7.26. Source: Google Workspace: Gmail SMTP errors and codes.

What usually causes it

  • A service sends as your domain without SPF or DKIM that matches your domain (a newsletter tool, a CRM, a booking system).
  • Forwarding or a mailing list changed the message, breaking its signature.
  • Someone else sent mail pretending to be you, and the bounce came back to you.
  • For 451: your domain's DNS servers are slow or failing.

How to fix it

  • Set up each sending service to pass SPF or DKIM with your own domain (most services call this domain authentication).
  • Never send from your own server with a gmail.com or yahoo.com From address.
  • For 451, fix your DNS hosting's reliability.
The free email check can find part of this

The free check shows your DMARC policy and your SPF and DKIM records. It can't see how a particular message matched them.

Run the free email check

Want it fixed? Our email deliverability packages start at $49 for an audit and plan. Other error codes.