What exchange message tracking interface can I use for a small organization?

Hallo!
I am having several workers with each one of them provided with an email address configured using Microsoft Office Outlook. Since a number of them are able to exchange emails with clients, I would like to get an exchange message tracking interface so that I am able to get notifications whenever there are any email exchanges. Like this I will stay up to date on the goings on in the office. Thanks.
