550 5.7.26 Gmail bounce: blocked by dmarc policy
What 550 5.7.26 means
Gmail rejected the message because it was unauthenticated and the sender's DMARC policy tells receivers to reject unauthenticated mail.
Message text
Unauthenticated email from domain-name is not accepted due to domain's DMARC policy.
Common causes of 550 5.7.26
- SPF and DKIM both fail for the From domain
- DMARC policy is p=reject and no aligned SPF or DKIM pass exists
How to fix 550 5.7.26
- Run DMARC checker on the From domain to see the policy.
- Run SPF checker and confirm every sending service is in the SPF record.
- Run DKIM checker to confirm a DKIM signature exists for the From domain.
- Make the SPF or DKIM domain align with the From domain (DMARC checker).
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How to read 550 5.7.26
The first part, 550, is the SMTP reply code. Requested action not taken, mailbox unavailable: the mailbox does not exist, is not allowed, or the message was refused for policy reasons. Replies that start with 4 are temporary and replies that start with 5 are permanent (RFC 5321 §4.2.1).
The second part, 5.7.26, is an enhanced status code (RFC 3463 §2) written class.subject.detail. Class 5 is a Permanent failure (5xx): the command was rejected and the sender should not repeat it unchanged (RFC 5321 §4.2.1; RFC 3463 §2).. Subject 7 is security or policy: authentication, authorization or policy refused the message. The detail number refines the subject, and providers may define details of their own, which is why one code can read differently at Gmail, Microsoft and Yahoo.
Do not keep resending the same message: a permanent failure repeats until the cause is fixed. Correct the cause, then send a new message.
Official source: knowledge.workspace.google.com. Last verified 2026-10-20.
Related guides
- DMARC fails even though SPF and DKIM pass: fixing alignment
- How to create an SPF record (syntax and examples)
- How DKIM works and how to publish a DKIM record
Related codes
- 5.7.26 SMTP: authentication failed
- 550 5.7.26 Gmail: no spf or dkim pass
- 550 5.7.26 Gmail: SPF hard fail
- 5.7.0 SMTP: security status
- 5.7.1 SMTP: delivery not authorized
- 5.7.23 SMTP: SPF validation failed
FAQ
What does 550 5.7.26 mean?
Gmail rejected the message because it was unauthenticated and the sender's DMARC policy tells receivers to reject unauthenticated mail. This is a permanent failure.
How do I fix 550 5.7.26?
Run DMARC checker on the From domain to see the policy. Run SPF checker and confirm every sending service is in the SPF record. Run DKIM checker to confirm a DKIM signature exists for the From domain. Make the SPF or DKIM domain align with the From domain (DMARC checker).
Is 550 5.7.26 permanent, and should I retry?
550 5.7.26 is a permanent failure, so retrying the same message will fail again. Fix the cause first, then send a new message.