Resources
There are several key steps that have to be addressed during this resource forest migration process to ensure a successful transition with minimal impact to the user community. Binary Tree specializes in email migrations, and we have helped both small 
and enterprise customers through their transition to an Exchange 2010 resource forest. The sequential process steps I will cover in this blog article include the following:
- Create a Matching Mail-Enabled Account in the Target AD Forest (resource forest)
- Perform Cross-Forest (inter-org) Mailbox Migration from Source to Target
- Capture and Store ALL Exchange Account Attributes on the Target Account
- Disable the Account in the Target AD Forest (resource forest)
- Disable the Mailbox on the Target Account (which literally breaks the connection from AD with this new mailbox and leaves it in an orphan state)
- Link the Source AD Account to the Target Mailbox in new resource forest
- Re-stamp All Exchange Email Account Attributes back to the Target Account, such as the Source Legacy Exchange Distinguished Name (DN) which is needed for Outlook delegates, plus proxy addresses, etc.)
- Provide Roll-Back Process to Migrate User Mailboxes Back to Original Source (just in case you need to use it)
As you can see from the list items above this process is NOT something easily performed by an inexperienced administrator. Let me go into a little more detail on each of these steps and you will understand why using an automated migration management solution like E2E Complete will save you a lot of headaches.