Hi,
As ZaZa said, you can use Exmon to check these 10 users if you use Exchange 2003, 2007 or 2010.
ExMon enables administrators to view and analyze how individual users affect the health and performance of an Exchange server, including CPU usage and network traffic. It also enables administrators to view and analyze how those individual users' experience
is affected by the server.
What's more, here is a thread for your reference.
Microsoft Exchange Server User Monitor
http://technet.microsoft.com/en-us/library/bb508855(v=exchg.65).aspx
Hope it helps.
Best regards,
Amy Wang
TechNet Community Support
