Gmail 421 4.7.40
Rate limited: no DMARC policy
Gmail 421 4.7.40 means: rate limited: no DMARC policy. It is a temporary failure, so your server retries it. Gmail requires bulk senders to publish DMARC. Add a TXT record at _dmarc on the From domain with at least p=none.
Gmail’s exact wording
Quoted from Google Workspace Admin Help: Gmail SMTP errors and codes, checked 2026-11-05. Placeholders are Gmail’s own.
Reply text
Your email has been rate limited because the sending domain doesn't have a DMARC record, or the DMARC record doesn't specify a DMARC policy. Gmail requires all bulk email senders to add a DMARC record to their sending domain. See Set up DMARC. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.
| Who sends it | Gmail and Google Workspace |
|---|---|
| Basic code | 421: <domain> Service not available, closing transmission channel (RFC) |
| Enhanced code | 4.7.40: Gmail-specific, not in the IANA registry. Its subject digit puts it under 5.7.0 other or undefined security status. |
| Permanent or temporary | Temporary (4xx) |
| Verifying the list prevents it | No |
In practice
Bulk senders to Gmail must publish a DMARC record on the From domain. A record with p=none is enough to meet the requirement. This deferral means Gmail found no DMARC record, or one without a policy tag. Add a TXT record at _dmarc.yourdomain.com such as v=DMARC1; p=none; rua=mailto:[email protected]. A DMARC record with p=none changes nothing about how your mail is treated; it only meets the requirement and starts reports.
What the sender should do
Gmail requires bulk senders to publish DMARC. Add a TXT record at _dmarc on the From domain with at least p=none.
Would verifying the list have prevented Gmail 421 4.7.40?
No
This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
Common questions
- What does Gmail 421 4.7.40 mean?
- Gmail 421 4.7.40 means: rate limited: no DMARC policy. It is a temporary failure, so your server retries it. Gmail requires bulk senders to publish DMARC. Add a TXT record at _dmarc on the From domain with at least p=none.
- Should I retry after Gmail 421 4.7.40?
- Your sending server retries it automatically, because it is a temporary (4xx) failure. Investigate only if it keeps coming back over several hours.
- Would verifying my list have prevented Gmail 421 4.7.40?
- No. This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
Sources
- Google Workspace Admin Help: Gmail SMTP errors and codes (checked 2026-11-05)
- RFC 5321: Simple Mail Transfer Protocol, section 4.2.3 (reply codes) (checked 2026-11-05)
Registry and provider wording is quoted exactly; guidance is written by the SimpleVerifier Team.
SimpleVerifier Team · Last checked against the sources 2026-11-05