451 4.7.1: Temporary Auth / Policy Hold
The 451 4.7.1 soft bounce is a temporary deferral, often greylisting or a DMARC-related hold. Learn how greylisting works and when to retry.
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451
4.7.1
Temporary Auth / Policy Hold
Common
🔢 Enhanced Status Code Breakdown: 4.7.1
| Component | Value | Meaning |
|---|---|---|
| Class | 4 | Temporary failure (Soft bounce) |
| Subject | 7 | Security or policy |
| Detail | 1 | Temporary Auth / Policy Hold |
Per RFC 3463 Enhanced Mail System Status Codes. Class (X) = severity, Subject (Y) = category, Detail (Z) = specific condition.
💬 What This Error Means
Your email is being held at the 'gate' for a safety check. This is often 'greylisting,' a trick servers use to stop bots. A real mail server (like yours) will try again in a few minutes, but a spam bot usually won't bother.
Common Causes
- Greylisting (the server wants to see if you're persistent)
- A temporary hold while the server double-checks your DMARC records
- A brief rate-limit while you send a batch of messages
How to Fix This
- Don't worry. Your server will automatically try again, and the second attempt will almost always work
- Make sure your SPF, DKIM, and DMARC are set up correctly to minimize these delays
📚 Official Documentation
Microsoft 365 uses 451 4.7.1 for DMARC-related temporary deferrals. Fixing alignment usually resolves it.
📖 Microsoft 365 / Outlook documentation → Browse all Microsoft 365 / Outlook error codes →📋 Real-World Example Messages
These are real bounce message formats you might receive. Paste yours into the Bounce Decoder for instant analysis.
451 4.7.1 Greylisting in action, please come back later 451 4.7.1 Service unavailable - try again later
🔗 Related Error Codes
🔧 Related Diagnostic Tools
These tools can help you diagnose and fix this type of bounce:
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