421 4.7.0: low domain reputation
Gmail has turned away this message because the domain it comes from has a very low reputation with Gmail.
- Gmail
- Provider
- Temporary (4xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 421 4.7.0
- Provider
- Gmail and Google Workspace
- Temporary or permanent
- TemporaryThe sending server keeps the message and tries again later.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
421 4.7.0 This message is suspicious due to the very low reputation of the sending domain.
What it means
Gmail keeps a reputation for sending domains as well as for IPs, built from how recipients react to mail that authenticates as that domain. Your domain is rated very low. Although the code is temporary, the wording says the message has been blocked, and similar mail will keep failing until the reputation improves. Moving to a new IP does not help, because the reputation follows the domain. Google documents the permanent form as 550 5.7.1 with nearly the same wording. Its sender guidelines FAQ asks senders to keep their spam rate below 0.1% and never let it reach 0.3%.
Common causes
- High spam complaint rates on mail from the domain.
- Mail sent to lists with many invalid or uninterested recipients.
- Authentication gaps that let others send as the domain, or that make your own mail fail checks.
- A new domain sending large volumes before it has any history.
How to fix it
- 01Check domain reputation and spam rate in Google Postmaster Tools.
- 02Cut volume to Gmail and send only to your most engaged recipients while the reputation recovers.
- 03Make sure SPF, DKIM and DMARC pass and align for every stream that uses the domain.
- 04Keep the user-reported spam rate below 0.1% and never let it reach 0.3%, the levels in Google's guidelines.
- 05Fix the sending practices before anything else; a fresh domain will end up in the same place.
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
- Email sender guidelines FAQ (Gmail Help)support.google.com
Related codes
- 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.
- 421 4.7.0Low IP reputation, rate limited.Gmail is rate limiting mail from your sending IP because that IP has a very low reputation with Gmail.
- 421Service not available.The receiving server is closing the connection and will not take mail right now. The reply is temporary, so the sending server keeps the message and tries again later.
- 5.7.0Security or policy refusal, unspecified.The message or session was refused for a security or policy reason that the server did not describe more precisely, or chose not to reveal.
Further reading
All 108 Gmail codesEvery code in the wikiPaste your own bounce