Besides, you can try to use Log Praser to analyze the message tracking log.
Process Tracking Log tool for Exchange Server 2007
b/exchange/archive/2008/02/07/3404839.aspx
Message Tracking tips in Exchange 2007 / Exchange 2010 using CMD lets
b/pepeedu/archive/2010/09/02/message-tracking-cmd-lets-in-exchange-2007-exchange-2010.aspx
Xiu Zhang
TechNet Community Support
I haven't had the time to setup the Log Parser and currently using powershell scripts isn't getting accurate information. I'm getting numbers from distribution groups multiple times so the sum of total recipients is off by a multiple of roughly 2 times..
What we do have is a good picture of the senders that are sending to thousands of recipients versus hundreds, so the priority of getting 100% accurate numbers has fallen.
Thanks for the input, if there are any more thoughts on getting a powershell command to get accurate results I'd like to see them.