550 5.7.1 Gmail bounce: likely unsolicited
What 550 5.7.1 means
Gmail blocked the message as likely spam. The rejection applies to this message and will repeat for similar mail.
Message text
This message is likely unsolicited email. To reduce the amount of spam sent to Gmail, this message has been blocked.
Common causes of 550 5.7.1
- Content looks like spam
- Sending IP or domain has a poor reputation
- Recipient list includes unsolicited addresses
How to fix 550 5.7.1
- Check your sending IP and domain with blocklist check.
- Check authentication with SPF checker, DKIM checker and DMARC checker.
- Improve list quality and content before sending again.
Check your domain
Check the SPF record of your sending domainRuns in your browser; nothing is uploaded.
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 5.7.1
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, 5.7.1, 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
- How to create an SPF record (syntax and examples)
- How DKIM works and how to publish a DKIM record
- How to set up a DMARC record, from p=none to p=reject
Related codes
- 5.7.1 SMTP: delivery not authorized
- 550 5.7.1 Microsoft: delivery not authorized
- 550 5.7.1 Microsoft: unable to relay
- 530 5.7.1 Microsoft: not authenticated
- 5.7.0 SMTP: security status
- 5.7.23 SMTP: SPF validation failed
FAQ
What does 550 5.7.1 mean?
Gmail blocked the message as likely spam. The rejection applies to this message and will repeat for similar mail. This is a permanent failure.
How do I fix 550 5.7.1?
Check your sending IP and domain with blocklist check. Check authentication with SPF checker, DKIM checker and DMARC checker. Improve list quality and content before sending again.
Is 550 5.7.1 permanent, and should I retry?
550 5.7.1 is a permanent failure, so retrying the same message will fail again. Fix the cause first, then send a new message.