Gmail 550 5.7.1
Blocked by policy, reputation or headers
Gmail 550 5.7.1 means: blocked by policy, reputation or headers. It is a permanent failure, so do not retry it unchanged. Gmail uses 550 5.7.1 for many permanent blocks: likely spam, very low IP or domain reputation, missing or duplicate headers, IPv6 without PTR and authentication, or a recipient policy. Read the exact text and fix the named cause before sending again.
Gmail’s exact wording
Quoted from Google Workspace Admin Help: Gmail SMTP errors and codes, checked 2026-11-05. Placeholders are Gmail’s own.
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The user or domain that you are sending to (or from) has a policy that prohibits the email that you sent. Contact your domain administrator for assistance. For more information, go to Sorry, a policy is in place that prevents your message from being sent.
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Invalid credentials for relay ip-address. The IP address you've registered in your Workspace SMTP Relay service doesn't match the domain of the account this email is being sent from. If you are trying to relay email from a domain that isn't registered under your Workspace account or has empty envelope-from:, you must configure your email server either to use SMTP AUTH to identify the sending domain or to present one of your domain names in the HELO or EHLO command. For more information, go to SMTP relay service error messages.
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This message is likely unsolicited email. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Why has Gmail blocked my messages?
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This message does not meet IPv6 sending guidelines regarding PTR records and authentication. For more information, go to Email sender guidelines.
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This message is likely suspicious due to the very low reputation of the sending IP address. To best protect our users from spam, the message has been blocked. For more information, go to Why has Gmail blocked my messages?
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This message is likely suspicious due to the very low reputation of the sending domain. To best protect our users from spam, the message has been blocked. For more information, go to Why has Gmail blocked my messages?
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Messages missing a valid address in the From: header, or having no From: header, are not accepted. For more information, go to Email sender guidelines and review RFC 5322 specifications.
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Messages missing a valid Message-ID: header are not accepted. For more information, go to Email sender guidelines and review RFC 5322 specifications.
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Messages with multiple addresses in the From: header are not accepted. For more information, go to Email sender guidelines and review RFC 5322 specifications.
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The message contains a unicode character in a disallowed header. To review our message and header content guidelines, go to File types blocked in Gmail.
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This message is not RFC 5322 compliant because it has duplicate headers. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.
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This message is not RFC 5322 compliant because the From: header is missing. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.
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This message is not RFC 5322 compliant because it has multiple From: headers. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.
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This message is not RFC 5322 compliant because the From: header has a non-compliant domain name. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.
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This email has been rate limited. For more information, go to Limits for sending & getting email.
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The IP you're using to send email is not authorized to send email directly to our servers. Use the SMTP relay at your service provider instead. For more information, go to 'The IP you're using to send email is not authorized...'.
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Daily SMTP relay sending limit exceeded for this customer. For more information on SMTP relay sending limits, contact your administrator or visit SMTP relay service error messages.
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Encoded-word syntax is not permitted in message header header-name. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.
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This message is not RFC 5322 compliant. There are multiple header-name headers. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.
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This message is not RFC 5322 compliant. There is a malformed header- name header. To reduce the amount of spam sent to Gmail, this message has been blocked. For more information, go to Email sender guidelines and review RFC 5322 specifications.
| Who sends it | Gmail and Google Workspace |
|---|---|
| Basic code | 550: Requested action not taken: mailbox unavailable (e.g., mailbox not found, no access, or command rejected for policy reasons) (RFC) |
| Enhanced code | 5.7.1: Delivery not authorized, message refused |
| Permanent or temporary | Permanent (5xx) |
| Verifying the list prevents it | Partly |
In practice
Gmail's reference lists twenty different 550 5.7.1 texts, more than any other code. They fall into four groups: spam and reputation blocks (likely unsolicited mail, low IP or domain reputation), header problems (missing or multiple From headers, missing Message-ID, duplicate headers, encoded words, unicode in a disallowed header), relay and IP problems (an IP not allowed to send directly, relay credential mismatches, relay limits), and recipient policy. The fix depends entirely on which sentence you have, so copy the full line from the bounce.
What the sender should do
Gmail uses 550 5.7.1 for many permanent blocks: likely spam, very low IP or domain reputation, missing or duplicate headers, IPv6 without PTR and authentication, or a recipient policy. Read the exact text and fix the named cause before sending again.
Would verifying the list have prevented Gmail 550 5.7.1?
Partly
The reply is not only about one address, but providers weigh how often a sender hits addresses that do not exist. Removing bad addresses before sending lowers that signal.
Common questions
- What does Gmail 550 5.7.1 mean?
- Gmail 550 5.7.1 means: blocked by policy, reputation or headers. It is a permanent failure, so do not retry it unchanged. Gmail uses 550 5.7.1 for many permanent blocks: likely spam, very low IP or domain reputation, missing or duplicate headers, IPv6 without PTR and authentication, or a recipient policy. Read the exact text and fix the named cause before sending again.
- Should I retry after Gmail 550 5.7.1?
- No. It is a permanent (5xx) failure, so the same message to the same address will fail again. Fix the cause first. Gmail uses 550 5.7.1 for many permanent blocks: likely spam, very low IP or domain reputation, missing or duplicate headers, IPv6 without PTR and authentication, or a recipient policy. Read the exact text and fix the named cause before sending again.
- Would verifying my list have prevented Gmail 550 5.7.1?
- Partly. The reply is not only about one address, but providers weigh how often a sender hits addresses that do not exist. Removing bad addresses before sending lowers that signal.
The same code elsewhere
Sources
- Google Workspace Admin Help: Gmail SMTP errors and codes (checked 2026-11-05)
- IANA: SMTP Enhanced Status Codes registry (checked 2026-11-05)
- RFC 5321: Simple Mail Transfer Protocol, section 4.2.3 (reply codes) (checked 2026-11-05)
Registry and provider wording is quoted exactly; guidance is written by the SimpleVerifier Team.
SimpleVerifier Team · Last checked against the sources 2026-11-05