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Permanent failure

550 5.7.26 Gmail: unauthenticated sender or DMARC failure

Quick answer

Gmail rejected the message because it failed authentication: neither SPF nor DKIM passed, or the message failed the DMARC policy of the domain in the From header. The recipient address is fine. The problem is the sending domain's setup.

Recommended action: Fix sender reputation

Common causes

  • The sending domain publishes no SPF record and the message is not DKIM signed.
  • The message is signed or sent by a platform whose domain does not align with the From domain, and the From domain has a DMARC policy of quarantine or reject.
  • Mail is sent with a gmail.com or other freemail From address through a third-party service.
  • An SPF record over the 10 DNS lookup limit, so SPF returns permerror.

What to do

Authenticate the domain in your From address. Publish one SPF record that includes every service that sends for you, turn on DKIM signing with your own domain, and publish a DMARC record. Check all three with our SPF, DKIM and DMARC checkers, then resend. Do not remove the recipient: the address is not the cause.

Provider note: Gmail also sends a temporary 421 4.7.26 version while rate limiting unauthenticated mail. RocketVerifier never sends mail, so this code only appears on your campaigns. If you see it in a bounce export, the address is still valid.

How to read 550 5.7.26

550 is the basic SMTP reply defined in RFC 5321. 5.7.26 is the enhanced status code from RFC 3463, which reads as class, subject and detail:

Class
5Permanent failure
Subject
.7Security or policy
Detail
.26Gmail: unauthenticated sender or DMARC failure

Further reading

FAQ

Frequently asked questions

Should I remove addresses that bounced with 550 5.7.26?

No. The rejection is about your sending domain's authentication, not the mailbox. Fix SPF, DKIM and DMARC and the same addresses will accept mail.

Does p=none fix 550 5.7.26?

Publishing DMARC is required for bulk senders, but the message also has to pass SPF or DKIM with a domain that aligns with your From address. A p=none record without aligned authentication does not stop the rejection.

Related bounce codes

All bounce codes

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