We have a client hosting with us as a shared hosting client with over 600 email user. Now they suspect some rogue employee is sending important and company internal information to outsiders by email. What they want is to have a facility to hold the mails (in+out both) on the server, examine it and then release or delete as the case may be. So is there a method to achieve this, we are open to all options whether its a cPanel/exim specific or any other MTA that we can host for him on an external VPS/server. We have already set unseen delivery method for him under system_filter, but this method does not stop information from leaving the server.