550 5.7.26 Gmail bounce: no spf or dkim pass
What 550 5.7.26 means
Gmail rejected the message because neither SPF nor DKIM passed for it. Gmail requires every sender to authenticate with at least one of them.
Message text
This email has been blocked because the sender is unauthenticated. Gmail requires all senders…
This is an excerpt: the provider's documentation shortens the message. Full text: provider documentation
Common causes of 550 5.7.26
- No SPF record, or the sending IP/service is not included in it
- Message is not DKIM-signed, or the signature does not verify
- Mail is sent through a service that was never authorised for the domain
How to fix 550 5.7.26
- Run SPF checker and confirm the sending IP or service is in the SPF record.
- Run DKIM checker to confirm the service signs with DKIM for your domain.
- Run DMARC checker: once SPF or DKIM passes and aligns, DMARC passes too.
- Paste the bounce headers into email header analyzer to see which check failed.
Check your domain
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Have the full bounce message? Paste it into the bounce code lookup and it will match the code and the provider for you. Open the bounce code lookup.
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: blocked by dmarc policy
- 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 neither SPF nor DKIM passed for it. Gmail requires every sender to authenticate with at least one of them. This is a permanent failure.
How do I fix 550 5.7.26?
Run SPF checker and confirm the sending IP or service is in the SPF record. Run DKIM checker to confirm the service signs with DKIM for your domain. Run DMARC checker: once SPF or DKIM passes and aligns, DMARC passes too. Paste the bounce headers into email header analyzer to see which check failed.
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.