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SMTP codes

SMTP 4.7.1 Temporary delivery not authorized

The server refuses for now by policy: greylisting, reputation or rate limits. Microsoft and Gmail use it for throttling.

4.7.1
Class
4xx · Temporary failure
Retried?
Yes, the sending server retries
Defined in
RFC 3463

What to do

How it appears in a bounce

450 4.7.1 Temporary delivery not authorized

Paste the full bounce into the decoder — it finds every code and recipient and says what to check.

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