There is a updated version of EPA so you can accurately analyze your existing Exchange environment.
Why would I use the EPA tool?
The value of the tool is the usage data extracted from your current Exchange 2003 or Exchange 2007 environment can be used for sizing your Exchange 2010 environment since the sizing calculator, for example, can leverage the mail profile data pulled from the EPA tool.
These are some of the values used to determine a sizing profile for the Exchange 2010 sizing tools.
Grab 32-bit version here
Grab 64-bit version here