Enhanced status code

SMTP error X.7.26

Multiple authentication checks failed

Updated Jul 1, 2026

The short answer

Multiple authentication checks failed Common cause: More than one authentication mechanism failed

Quick fix

Check SPF, DKIM, DMARC, and related authentication together

This code is written X.7.26 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 SPF, DKIM, DMARC, and related authentication together

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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