Exchange 2007 to Exchange 2010 Cross Forest

Hi

We have a scenario where we have an Exchange 2007 organization (Org A - Source) and a separate Exchange 2010 organization (Org B - Target). Both the organizations (AD Forests) have two way trusts between them. We want to have our Exchange 2007 users have their mailboxes hosted on Exchange 2010 organization. Meaning that the user (AD) accounts of Org A will remain in Forest A but there mailboxes will be available on Exchange 2010 servers in Org B. So we don’t need a user / group migration stuff here and mailbox data on Exchange 2007 servers is also not critical (not required to be migrated) so we will be creating new disabled accounts and mailboxes in Org B for each user in Org A and connect the mailboxes. There will be a brief period of co-existence between two Orgs (to enable mail-flow) until all the users have their mailboxes active in Org B. Need to figure out a way to achieve this.

We are planning to follow the steps below:

1. Setup name resolution between the forests (although basic connectivity is there and we can ping servers in one forest using IP Addresses from other forest) – Please suggest if this is necessary or we can get away with it?
2. Setup SMTP namespace sharing for Exchange 2007 SMTP Domain name
3. Add Exchange 2007 SMTP domain as authoritative domain to E2K10
4. Create EAP for new SMTP Domain
5.  SMTP Connector Creation for Direct E-mail Routing (Co-exist) Between Forests
6. Create disabled Mail Enabled (not Mailbox Enabled) User or Mail Enabled Contact in Org B.Can we use Prepare-MoveRequest.ps1 script to create these?
7. Once a mail enabled user / contact is created in Org B for all the users, change incoming traffic from Internet for Org A SMTP domain to hit HT server in Org B
8. Make changes to Exchange 2010 certificate and install new certificate
9. Select a batch of users every day, create new mailbox for them using scripts in Org B and delete the corresponding contact in Org B

Can someone please confirm if this is correct and point out something I am missing?

Is there any other way to achieve the same goal?

Thanks

Taranjeet Singh

zamn