I've updated the subversion repository of Kristof Coomans' eZMail Debug patch to work with eZ Publish 3.9.2
To use, simply download the patched ezmail.php from http://pubsvn.ez.no/community/trunk/hacks/ezmaildebug/patches/3.9.2/lib/ezutils/classes/ezmail.php
and save it to lib/ezutils/classes/ezmail.php of your eZ Publish 3.9.2 install.