Microsoft has released Microsoft Exchange Server User Monitor
Use the Microsoft Exchange Server User Monitor to gather real-time data to better understand current client usage patterns, and to plan for future work. Administrators can view several items, including IP addresses used by clients, versions and modes of Microsoft Office Outlook, and resources such as CPU usage, server-side processor latency, and total latency for network and processing. Works with Microsoft Exchange Server 2000, 2003, 2007 and 2010.Microsoft Exchange Server User Monitor
