Enhanced status code

SMTP error X.7.7

Message integrity failure

Updated Jul 1, 2026

The short answer

Message integrity failure Common cause: Message was corrupted or altered

Quick fix

Check signing, transport, and message modification

This code is written X.7.7 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 signing, transport, and message modification

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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