Enhanced status code

SMTP error X.3.4

Message too big for system

Updated Jul 1, 2026

The short answer

Message too big for system Common cause: Message exceeds receiving system's maximum size

Quick fix

Reduce message or attachment size

This code is written X.3.4 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

Reduce message or attachment size

Related codes

X.3.0 Other or undefined mail system status X.3.1 Mail system full X.3.2 System not accepting network messages X.3.3 System not capable of selected features X.3.5 System incorrectly configured X.3.6 Requested priority changed
All SMTP error codes
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