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Microsoft 365

550 5.7.509 “has a DMARC policy of reject”

The domain in the From address has a DMARC policy of reject, and this message failed DMARC, so Exchange Online refused it.

Codes: 550 5.7.509. Source: Microsoft Learn: Non-delivery reports in Exchange Online.

What usually causes it

  • Missing or incorrect SPF or DMARC records, or SPF that doesn't match the From domain.
  • The message isn't DKIM-signed, or the DKIM record is missing.
  • Forwarding that broke SPF or DKIM on the way.

How to fix it

  • Make every service that sends as your domain pass SPF or DKIM with your own domain.
  • Check that your DKIM key is published and signing is turned on in each service.
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.