Gmail 451 4.7.23
Rate limited: missing PTR record
Gmail 451 4.7.23 means: rate limited: missing PTR record. It is a temporary failure, so your server retries it. The sending IP has no PTR record, or the PTR name does not resolve back to the IP. Set matching reverse and forward DNS for the IP.
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
ip-address The sending IP address for this message doesn't have a PTR record, or the PTR record's forward DNS entry doesn't match the sending IP address. To protect users from spam, your email has been temporarily rate limited. To learn more about IP address requirements for sending to Gmail, visit the IP addresses section of our sender guidelines. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.
| Who sends it | Gmail and Google Workspace |
|---|---|
| Basic code | 451: Requested action aborted: local error in processing (RFC) |
| Enhanced code | 4.7.23: SPF validation failed |
| Permanent or temporary | Temporary (4xx) |
| Verifying the list prevents it | No |
In practice
Gmail checks that every sending IP has a PTR record whose name resolves back to the same IP. This temporary version rate-limits the mail; the permanent 550 5.7.25 blocks it. Self-hosted servers on cloud or VPS providers are the usual cases, because the default PTR names a generic host. Set the PTR through your hosting provider's control panel.
What the sender should do
The sending IP has no PTR record, or the PTR name does not resolve back to the IP. Set matching reverse and forward DNS for the IP.
Would verifying the list have prevented Gmail 451 4.7.23?
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 451 4.7.23 mean?
- Gmail 451 4.7.23 means: rate limited: missing PTR record. It is a temporary failure, so your server retries it. The sending IP has no PTR record, or the PTR name does not resolve back to the IP. Set matching reverse and forward DNS for the IP.
- Should I retry after Gmail 451 4.7.23?
- 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 451 4.7.23?
- 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)
- IANA: SMTP Enhanced Status Codes registry (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