How to Determine if You Are Running Exchange in Mixed or Native Mode
Running in mixed mode allows you to coexist with previous versions of Exchange, but it limits the functionality of your Exchange 2003 servers. This procedure explains how to determine if you are running in mixed or native mode.
Procedure
To determine the operating mode of your Exchange organization
In Exchange System Manager, right-click the Exchange organization for which you want to determine the operating mode, and then click Properties.
On the General tab, under Operation mode, the operating mode of your organization is displayed.