Messages Center
This link which is available in the top menu on all pages inside advertisers and publishers areas shows all messages sent from admin to the user and vice versa. URL's of the pages are advertiser.php?action=message_center and at publisher.php?action=message_center. You can use this feature to contact each individual user - a link to the form is in Administration on the user details table: "Create a new message for this user". Users can send messages to admin, the form is directly below the list of existing messages. This page uses the template shared_messages.html, there are available these variables:

#%messages%# | The list of messages. Each line in this list uses the template shared_messages_one_message.txt. Each of the lines contain the date and title of each message and also the info if it has been sent by admin or user and if it has been read already. When users click to the title of the message, it shows the complete message, this popup window uses the template shared_message.html.
#%title%# #%text%# | This is used in the "Send a New Message to Admin". These variables show title and text of the entered message, as far as some error occurred.

All these templates are used for advertisers as well as for publishers.