Enhanced status code

SMTP error X.7.29

ARC validation failure

Updated Jul 1, 2026

The short answer

ARC validation failure Common cause: ARC chain did not validate

Quick fix

Check ARC seals / signatures and intermediary modifications

This code is written X.7.29 because the reason is the same whether the failure is temporary (a 4 first digit) or permanent (a 5). Read the first digit of your own bounce to know which applies.

How to fix it

Check ARC seals / signatures and intermediary modifications

Related codes

X.7.0 Other or undefined security status X.7.1 Delivery not authorized X.7.2 Mailing list expansion prohibited X.7.3 Security conversion required but impossible X.7.4 Security features not supported X.7.5 Cryptographic failure
All SMTP error codes
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