Enhanced status code

SMTP error X.7.4

Security features not supported

Updated Jul 1, 2026

The short answer

Security features not supported Common cause: Receiver does not support requested security feature

Quick fix

Use a supported authentication / security method

This code is written X.7.4 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

Use a supported authentication / security 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.7.5 Cryptographic failure X.7.6 Cryptographic algorithm not supported
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