Enhanced status code

SMTP error X.3.0

Other or undefined mail system status

Updated Jul 1, 2026

The short answer

Other or undefined mail system status Common cause: Unspecified issue on destination mail system

Quick fix

Check the server response and retry if temporary

This code is written X.3.0 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 the server response and retry if temporary

Related codes

X.3.1 Mail system full X.3.2 System not accepting network messages X.3.3 System not capable of selected features X.3.4 Message too big for system X.3.5 System incorrectly configured X.3.6 Requested priority changed
All SMTP error codes
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