Have you ever wanted to know more than just that a new private message has arrived when your users submit items? How about, what they submitted and a quick link back to your administration panel? OK, here's what to do.
In your language file (for example, if using english, your /language/english.php file), change your _ON_NEW_CONTENT line to this (customize it how you like):
DEFINE('_ON_NEW_CONTENT', "Hello,\nA new content item has been submitted by [ %s ] titled [ %s ] for the section [ %s ] and category [ %s ].\nPlease go to $mosConfig_live_site/administrator/ to view and approve this article.\nPlease do not respond to this message as it is automatically generated and is for information purposes only." );
Then go in to /components/com_messages/messages.class.php, and delete these two lines (should be 84 and 85):
$subject = _NEW_MESSAGE; $msg = _NEW_MESSAGE;
Then, in the next line (formerly 87), change $msg to $message, like so:
mosMail($mosConfig_mailfrom, $mosConfig_fromname, $recipient, $subject, $message);
This will make it email using the same subject and message line that is in the private message.