Enhanced status code

SMTP error X.3.1

Mail system full

Updated Jul 1, 2026

The short answer

Mail system full Common cause: Destination server storage is exhausted

Quick fix

Retry later

This code is written X.3.1 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

Retry later

Related codes

X.3.0 Other or undefined mail system status 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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