Enhanced status code

SMTP error X.7.11

Encryption required for authentication mechanism

Updated Jul 1, 2026

The short answer

Encryption required for authentication mechanism Common cause: Selected AUTH method cannot be used without encryption

Quick fix

Connect using TLS or choose another AUTH method

This code is written X.7.11 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

Connect using TLS or choose another AUTH method

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
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