In order to test this, you need to replicate an attempt to send message using non-existing component or provider name. For example, you may modify file message/lib.php the way: --- a/message/lib.php +++ b/message/lib.php @@ -2006,7 +2006,7 @@ function message_post_message($userfrom, $userto, $message, $format) { $eventdata = new stdClass(); $eventdata->component = 'moodle'; - $eventdata->name = 'instantmessage'; + $eventdata->name = 'instantmessage_'; $eventdata->userfrom = $userfrom; $eventdata->userto = $userto; Now try to send personal message to another user, upon the click "Send message", you will get coding exception that will contain the preference name causing error: Coding error detected, it must be fixed by a programmer: Could not load preference popup_provider_moodle_instantmessage__permitted. Does the component and name you supplied to message_send() match a row in message_providers? Message providers must appear in the database so users can configure how they will be notified when they receive messages.