4.7.1: Temporarily refused (often greylisting)
4.7.1 is the temporary form of "delivery not authorized". Many servers send 451 4.7.1 for greylisting: they reject the first attempt from an unfamiliar sender and accept a correct retry a few minutes later. A real mail server retries automatically; a script that never retries will lose the message.
The exact message
Any mail server (RFC standard meaning)
4.7.1 Delivery not authorized, message refused
Why it happens
- Greylisting: the receiver defers mail from sender and IP combinations it has not seen before.
- A temporary policy or reputation check on the receiver.
How to fix it
- Make sure your sending software retries temporary failures, as standard mail servers do.
- If it never clears, read the text after the code; it may be a reputation deferral.
If you send cold email
Tools that send through a real mailbox provider retry automatically. Custom scripts that treat a 4xx as final will silently drop mail to greylisting servers.
How WarmHawk handles it
WarmHawk never sends more than a mailbox’s own daily cap, spaces sends from one mailbox at least 8 minutes apart with random jitter, and starts a newly warmed mailbox at 5 campaign emails a day, growing 20% a day. A temporary failure is retried with backoff (30 minutes, then doubling) and the lead is suppressed after 4 attempts, so a throttled mailbox is never hammered. How WarmHawk works →
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Related bounce codes
Sources, checked 2026-09-29: RFC 3463: Enhanced Mail System Status Codes · RFC 6647: Email Greylisting. Have a different bounce? Paste it into the decoder →
Questions
4.7.1 questions
What does 4.7.1 mean?+
4.7.1 is the temporary form of "delivery not authorized". Many servers send 451 4.7.1 for greylisting: they reject the first attempt from an unfamiliar sender and accept a correct retry a few minutes later. A real mail server retries automatically; a script that never retries will lose the message.
Is 4.7.1 a temporary or permanent error?+
Temporary. The sending server keeps the message and retries it for a while. It only becomes a bounce if every retry fails before the message expires.
How do I fix 4.7.1?+
Make sure your sending software retries temporary failures, as standard mail servers do. If it never clears, read the text after the code; it may be a reputation deferral.