After many weeks of writing, reviewing, and updating, I finally finished a whitepaper the describes all of the user accounts, security groups, MPF permissions, and SQL roles utilized by the Microsoft Solution for Hosted Messaging and Collaboration 3.0. The goal of the paper is NOT to tell you how to set those properties, but it shows you what your Active Directory objects and permissions should look like after you've deployed a HMC 3.0 successfully.
Here is a link where you can dowload the whitepaper: http://www.go-planet.com/ser_tech.asp
Enjoy!
Conrad
BTW: If you have feedback on the document, please feel free to email me directly at conrada@go-planet.com. I'll make updates to the document as need.