How to move mailbox from legacy Exchange forest to Exchange 2010 forest

In Exchange 2010, before moving a mailbox cross-forest, it is necessary to ensure the corresponing AD account has been moved to the target forest. Otherwise, the mailbox move process failes. So, the following steps focus on how to move AD accounts from the legacy Exchange forest to the Exchange 2010 forest and then how to move mailboxes afterwards.

Step 1: Move AD account

Note: Please perform the following steps in the target forest where Exchange 2010 server is installed.

1. Open Exchange Management Shell, and navigate to the folder where the Prepare-MoveRequest.ps1 script stores.

2. Type the following command and press Enter:

$cred = Get-Credential

Note: You will receive a pop-up window for entering the credential. Please enter the credential of the Administrator account in the source forest.

.\Prepare-MoveRequest.ps1 -Identity <e-mail address> -RemoteForestDomainController <FQDN of DC in source forest> -TargetMailUserOU <OU name> -RemoteForestCredential $cred

Note: Please replace <e-mail address> with the e-mail address of an AD account in the source forest.

Step 2: Enable AD account

After performing Step 1, a disabled AD account will be created in Exchange 2010 forest and it is a Mail User account as well. Please enable the disabled AD account in Active Directory Users and Computers.

Step 3: Move Mailbox cross forest

Run the following cmdlet in Exchange 2010 forest to move the mailbox:

New-MoveRequest -Identity <e-mail address of the mailbox in source forest> -RemoteLegacy -TargetDatabase "<database name>" -RemoteGlobalCatalog "<GC in source forest>" RemoteCredential $cred -TargetDeliveryDomain domain.com

[How to move the AD accounts in bulk]

a. Create a .csv file (e.g. C:\transition.csv) to include the following information:

EmailAddress

User1@olddomain.com

User2@olddomain.com

b. Open Exchange Management Shell and run the following cmdlet:

Note: After opening Exchange Management Shell, please first navigate to the folder where the Prepare-MoveRequest.ps1 script stores.

$cred = Get-Credential

Note: You will receive a pop-up window for entering the credential. Please enter the credential of the Administrator account in the source forest.

Import-CSV "C:\transition.csv" | ForEach-Object -Process {.\Prepare-MoveRequest.ps1 -Identity $_.EmailAddress -RemoteForestDomainController<FQDN of DC in source forest> -TargetMailUserOU <OU name> -RemoteForestCredential $cred}

[How to move mailboxes cross-forest in bulk]

a. Create the transition.csv file include the following information:

EmailAddress

User1@olddomain.com

User2@olddomain.com

b. Run the following cmdlet:

$cred = Get-Credential

Note: You will receive a pop-up window for entering the credential. Please enter the credential of the Administrator account in the source forest.

Import-CSV "C:\transition.csv" | ForEach-Object -Process {New-MoveRequest -Identity $_.EmailAddress -RemoteLegacy -TargetDatabase "<database name>" -RemoteGlobalCatalog "<GC in source forest>" RemoteCredential $cred -TargetDeliveryDomain domain.com}

In addition, during the whole procedure, there is no need to build the trusts between forests as long as you know the credential of the Administrator of the source forest and target forest.

Regarding the Prepare-MoveRequest.ps1 script I mentioned above, it can be downloaded from the following link:
Prepare for Online Mailbox Move

http://www.microsoft.com/downloads/details.aspx?FamilyID=16a91d42-5ca4-4b58-aaa6-b2689b99ba51&displaylang=en