Gmail temporary SPF deferral
Fix Gmail 421 4.7.27 SPF rate limiting
Gmail returns 421 4.7.27 when a bulk-sender message did not pass SPF and is temporarily rate limited. Evaluate the IP against the exact MAIL FROM domain shown in Google's result.
The response includes:
421 4.7.27 Your email has been rate limited because SPF authentication didn't pass for this message.
Check the current SPF sender path
421 is temporary. Preserve queued retries with backoff, but correct a confirmed SPF failure before generating more traffic.
Why SPF did not pass
- The sender IP is absent from the evaluated policy.
- The actual MAIL FROM subdomain has no SPF record or a different record.
- A provider include is missing, broken, or placed after terminating
all. - Multiple SPF records or an evaluation error prevents a valid result.
- The wrong service or IP is sending mail for the domain.
How to fix Gmail 421 4.7.27
- Copy Google's domain and IP from the complete response.
- Confirm that the IP belongs to an intended sender.
- Evaluate the selected policy at that exact MAIL FROM domain.
- Add only the provider's documented authorization while preserving other legitimate senders.
- Wait for DNS visibility, then send one fresh test and inspect the new result.
Frequently asked questions
What does Gmail 421 4.7.27 mean?
Gmail temporarily rate limited a bulk-sender message because SPF did not pass for the stated domain and sending IP.
Is the visible From domain always the SPF domain?
No. SPF evaluates the envelope MAIL FROM domain, which can differ from the visible From domain.
Will retrying fix the SPF record?
No. Retrying is correct for the temporary response, but a persistent sender-path authorization problem must still be corrected.
Related email diagnostics
Primary sources: Gmail SMTP errors and codes and RFC 7208 SPF.