Adding additional template items to the template. There are a few places to edit.
plugins/cerberusweb.core/api/listeners.classes.php around line 530.
and
api/app/Parser.php around line 671
Code from listeners.classes.php but both code is similar.
CerberusMail::sendTicketMessage(array(
'ticket_id' => $ticket->id,
'message_id' => $ticket->first_message_id,
'content' => str_replace(
array('#ticket_id#', '#mask#','#subject#','#timestamp#','#sender#','#sender_first#','#orig_body#'),