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.
4.7.1
| Component | Value | Meaning |
|---|---|---|
| Class | 4 | Persistent transient failure (temporary) |
| 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.
Your email is being temporarily deferred due to a policy or authentication check. This often relates to greylisting or a DMARC-related deferral — retrying usually succeeds.
Microsoft 365 uses 451 4.7.1 for DMARC-related temporary deferrals. Fixing alignment usually resolves it.
📖 Microsoft 365 / Outlook documentation →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
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