550 5.7.1: blocked as likely spam
Gmail's filters judged this message likely to be spam and rejected it outright, instead of delivering it to the spam folder.
- Gmail
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550 5.7.1
- Provider
- Gmail and Google Workspace
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
550 5.7.1 This message is likely unsolicited email.
What it means
Gmail's filters weighed the message, its links and its sender's history, and decided it is likely unsolicited. Gmail moves much suspected spam to the spam folder, but it blocks some messages that look like spam, and this is the reply it sends when it does. Google links it to its help article on how Gmail blocks messages, which says a message might be blocked if it contains words that look like spam or if the sender has a history of sending spam. Look at the message and at the sending practices behind it.
Common causes
- Content or links typical of spam or phishing.
- A sender with a history of spam complaints.
- Mail sent to recipients who did not ask for it.
- Missing or failing authentication.
How to fix it
- 01Check your domain and IP reputation and your spam rate in Google Postmaster Tools.
- 02Confirm that SPF, DKIM and DMARC pass and align.
- 03Review the message for spam-like wording, link shorteners and links to poorly rated domains.
- 04Send only to people who opted in, and offer one-click unsubscribe.
- 05Test changes on a small group before sending widely.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Gmail SMTP errors and codes (Google Workspace Admin Help)knowledge.workspace.google.com
- Learn how Gmail blocks your messages (Gmail Help)support.google.com
Related codes
- 550 5.7.1Blocked for low IP reputation.Gmail permanently rejected the message because the IP it came from has a very low reputation with Gmail.
- 550 5.7.1Blocked for low domain reputation.Gmail permanently rejected the message because the domain it comes from has a very low reputation with Gmail.
- 550Mailbox unavailable.The receiving server permanently refused the message for this recipient: the mailbox does not exist, cannot be reached, or the server rejected the message by policy.
- 5.7.1Delivery not authorised.The receiving server refuses the message because this sender is not allowed to send to this recipient, as a result of filtering by host or by recipient.
5.7.1 at other providers
- 550 5.7.1Not authorized to send to this recipient.You do not have permission to send to this recipient, typically a group restricted to certain senders or a recipient protected by a mail flow rule.
- 550 5.7.1Public folder does not accept external mail.An external sender wrote to a mail-enabled public folder in Microsoft 365, which by default accepts mail only from authenticated senders.
- 550 5.7.1Sending IP blocked by Proofpoint Dynamic Reputation.Proofpoint’s IP reputation system has your sending IP on its block list because it has seen spam or viruses from it, so Proofpoint customers refuse your mail.
- 550 5.7.1SPF check failed.The recipient’s Cisco Secure Email gateway checked SPF, found your server not authorised for the sender domain, and its policy rejects that result.
- 550 5.7.1Rejected under your domain’s DMARC policy.Your message failed DMARC, your domain’s DMARC record asks receivers to reject such mail, and the recipient’s Cisco gateway did so.
- 550 5.7.1DMARC verification failed permanently.The Cisco gateway hit a permanent failure while verifying DMARC for your message, and the recipient’s policy rejects such mail. Cisco does not say what produces that failure.
Further reading
All 108 Gmail codesEvery code in the wikiPaste your own bounce