421 4.7.0: suspicious content or links
Gmail blocked this message because something in its text or its links looks like spam or abuse to Gmail's filters.
- 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 nature of the content or the links within.
What it means
Here the problem is the message rather than the sender. Gmail's filters found the content, or one of the links, suspicious, so the message has been blocked even though the reply carries a temporary code. Links are a frequent trigger: a URL shortener, a domain with a poor reputation or a Safe Browsing listing, or a tracking domain shared with spammers. Google's sender guidelines ask senders to check that their domain is not listed as unsafe in Google Safe Browsing, and to check the status of domains linked to theirs. Retrying the same message is unlikely to help; change the content first.
Common causes
- A link to a domain with a poor reputation or a Safe Browsing listing.
- Public URL shorteners or redirect chains that hide the real destination.
- Content that resembles phishing or spam, such as urgent payment requests or misleading subject lines.
- Attachments or link patterns that Gmail associates with malware.
How to fix it
- 01Check every linked domain, including tracking and image hosts, on Google's Safe Browsing site status page.
- 02Replace URL shorteners with full links on a domain you control.
- 03Remove or rewrite content that reads like phishing, and test the revised message on a small group first.
- 04If your sending provider gives you a shared click-tracking domain, switch to one of your own.
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 (Gmail Help)support.google.com
Related codes
- 421 4.7.28Unsolicited mail containing your link domain.Gmail is rate limiting messages that link to one of your domains, because that domain appears in an unusual rate of unsolicited mail.
- 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