Hi all,

As describe here => http://php.net/manual/en/mbstring.constants.php
This constant must be compiled into PHP or dynamically loaded at runtime.
But some free webhost, do not compile it or dymamically load it.

So it result the following notice when DEBUG_EXTRA is enabled

[phpBB Debug] PHP Notice: in file [ROOT]/includes/acp/acp_main.php on line 631: Use of undefined constant MB_OVERLOAD_MAIL - assumed 'MB_OVERLOAD_MAIL'

Regards.