Will I be able to monitor the traffic (emails) from the users of the 3 sub accounts?

Also will I be able to access these sub accounts once I have allocated them to each of the users?

I.e If user one changes the password of his account, will I still be able to access it and send emails from it? or at least control it from the Super Administrator account. 

The Dashbord/Control Panel do not seem to offer this kind of "close" control. 

What is the solution or how do you manage this?