421 4.7.27: SPF did not pass, rate limited
Gmail is rate limiting your mail because it failed SPF, which Gmail requires of bulk senders, those sending more than 5,000 messages a day to Gmail.
- Gmail
- Provider
- Temporary (4xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 421 4.7.27
- 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 4.7.27 Your email has been rate limited because SPF authentication didn't pass for this message.
What it means
Google's sender guidelines require anyone sending more than 5,000 messages a day to Gmail accounts to pass both SPF and DKIM. This message failed SPF: the sending IP named in the bounce is not authorized by the SPF record of the envelope sender (Return-Path) domain. It is the temporary form, also listed in Google's sender guidelines FAQ; the permanent form is 550 5.7.27. SPF checks the envelope domain, which may be your sending provider's bounce domain rather than the domain your readers see, so look up the right one.
Common causes
- The sending IP or service is missing from the SPF record of the envelope domain.
- The SPF record has a syntax error or needs more than ten DNS lookups, so it returns an error.
- Mail is forwarded or relayed through a server the SPF record does not list.
How to fix it
- 01Find the envelope domain and the IP in the bounce, and check that domain's SPF record with an SPF lookup.
- 02Add the missing sending service or IP range to the record.
- 03Keep the record within ten DNS lookups and remove services you no longer use.
- 04Make the envelope domain align with your From domain so the SPF pass also counts for DMARC.
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
- Email sender guidelines (Gmail Help)support.google.com
Related codes
- 550 5.7.27SPF did not pass, blocked.Gmail rejected the message because it failed SPF, which Gmail requires of bulk senders along with DKIM.
- 421 4.7.30DKIM did not pass, rate limited.Gmail is rate limiting your mail because it failed DKIM, which Google requires of bulk senders along with SPF.
- 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.
Further reading
All 108 Gmail codesEvery code in the wikiPaste your own bounce