451
451 Unresolvable From Domain
Yahoo could not resolve the visible From domain and deferred the message.
A missing DNS zone, expired domain, or incomplete propagation can trigger this soft bounce. Once DNS is healthy, Yahoo accepts the traffic.
Severity
WARNING
Provider
Yahoo Mail
Last Reviewed
2025-06-01
How to Fix 451
Follow these steps to resolve this Yahoo Mail SMTP error and restore normal delivery.
- ✓Verify A, MX, and TXT records for the From domain resolve globally.
- ✓Confirm the domain registration is active and not in redemption.
- ✓Avoid newly delegated domains until DNS propagation finishes.
- ✓Fallback to a proven From domain while the issue is resolved.
Helpful Resources
More Yahoo Mail SMTP Codes
Keep these related troubleshooting guides handy while addressing 451.
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