Create and manage a cross-tenant migration batch

To migrate mailboxes and related data from one Microsoft 365 tenant to another, you can follow these steps to create and manage a cross-tenant migration batch effectively and efficiently.

Step 1: Prepare the Source and Target Tenants

Before initiating the migration, ensure that both the source and target tenants are properly set up. This includes verifying domain ownership, configuring user accounts, and establishing the necessary permissions for migration. Ensure that both tenants have the required licenses for the migration process.

Step 2: Set Up Permissions and Trust

To grant permissions and establish trust between the source and target tenants, create and configure a security principal in both tenants. This security principal will allow access to mailboxes during the migration process. The required permissions include ApplicationImpersonation and FullAccess.

Here’s an example of PowerShell code to create a security principal using the New-ManagementRoleAssignment cmdlet:

New-ManagementRoleAssignment -Role "ApplicationImpersonation" -User "MigrationAdmin" -CustomRecipientWriteScope "Migration"

Step 3: Create the Migration Endpoint

In the target tenant, set up a migration endpoint that connects to the source tenant. This endpoint allows secure communication between the two tenants for mailbox migration. You can create a migration endpoint using the Exchange admin center (EAC) or PowerShell.

Here’s an example of PowerShell code to create a migration endpoint:

New-MigrationEndpoint -IMAP -Name "SourceEndpoint" -RemoteServer 'source.imapserver.com' -ConnectionSettings $connectionSettings -Authentication Basic

Step 4: Create the Migration Batch

Create a migration batch to specify the mailboxes to migrate and the target destination. A migration batch is a logical grouping of mailboxes that can be managed together during the migration process. You can create a migration batch using the Exchange admin center or PowerShell.

Here’s an example of PowerShell code to create a migration batch:

New-MigrationBatch -Name "CrossTenantBatch" -SourceEndpoint 'SourceEndpoint' -TargetDeliveryDomain 'target-domain.com' -CSVData ([System.IO.File]::ReadAllBytes("C:\MigrationData\migrate.csv"))

In this example, “migrate.csv” is a CSV file containing mailbox details, such as email addresses and aliases, for the mailboxes you want to migrate.

Step 5: Start and Monitor the Migration

Once the migration batch is created, you can start the migration process. Use the Start-MigrationBatch cmdlet to begin the migration. It’s essential to monitor the migration progress to ensure it completes successfully.

Here’s an example of PowerShell code to start a migration batch:

Start-MigrationBatch -Identity "CrossTenantBatch"

To monitor the status of the migration batch, you can use the Get-MigrationBatch cmdlet.

Step 6: Complete the Migration

After the migration batch finishes processing, perform additional steps to complete the migration. This typically involves updating DNS records, rerouting email traffic, and verifying the functionality of the migrated mailboxes.

Step 7: Remove the Migration Batch

Once the migration is complete and verified, remove the migration batch and related migration data. Use the Remove-MigrationBatch cmdlet for this purpose.

Here’s an example of PowerShell code to remove a migration batch:

Remove-MigrationBatch -Identity "CrossTenantBatch" -Confirm:$false

By following these steps, you can successfully create and manage a cross-tenant migration batch in Microsoft 365 Messaging. Refer to Microsoft documentation for more detailed guidance and additional options for managing the migration process.