Minor When send a direct message to other user (for example: message/index.php?user=2&id=3) with mail debug enable, Moodle return the following error:
SyntaxError: Unexpected token < in JSON at position 0
at parse (<anonymous>)
at Nb (http://XXXXXXX/moodle/lib/javascript.php/1509435798/lib/jquery/jquery-3.1.0.min.js:1:74037)
at A (http://XXXXXXX/moodle/lib/javascript.php/1509435798/lib/jquery/jquery-3.1.0.min.js:1:77562)
at XMLHttpRequest.<anonymous> (http://XXXXXXX/moodle/lib/javascript.php/1509435798/lib/jquery/jquery-3.1.0.min.js:1:80166)
In addition, message page not refresh correctly and remain wiht message "disable": Unable to render embedded object: 
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