Enhanced status code

SMTP error X.7.25

Reverse DNS validation failed

Updated Jul 1, 2026

The short answer

Reverse DNS validation failed Common cause: Sending IP failed the receiver's PTR / rDNS check

Quick fix

Configure valid PTR and matching forward DNS

This code is written X.7.25 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

Configure valid PTR and matching forward DNS

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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