Product research question: Report on emails from all company inboxes?

Hi,

I'm looking for any products out that solve this problem:

I want to know which of my customers email which employee, and how soon they get replied to. This will tell me who in my company has the strongest relationship with a given customer, and alert me if an employee is taking too long to get back to a customer.

What product can I use to do this?

I imagine the solution would be something that bolts on to Exchange and monitors all inbound / outbound messages, but maybe it would take a different form all together.