SMTP codes
SMTP 4.7.0 Temporary security or policy failure
A temporary policy refusal: greylisting, rate limit, TLS problem, or a reputation check. Gmail uses 421 4.7.0 for unusual rate or suspicious traffic.
- Class
- 4xx · Temporary failure
- Retried?
- Yes, the sending server retries
- Defined in
- RFC 3463
What to do
- Let it retry; slow down sending.
- Check SPF, DKIM, DMARC and PTR: Gmail and Microsoft throttle unauthenticated mail.
How it appears in a bounce
450 4.7.0 Temporary security or policy failure
Paste the full bounce into the decoder — it finds every code and recipient and says what to check.