Increase the Number of Mailboxes to Migrate Simultaneously

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Applies to: Office 365 for enterprises, Live@edu

When you use the Exchange Control Panel to create a migration batch, you have to specify the number of mailboxes to migrate at the same time by configuring the Number of mailboxes to migrate simultaneously field. In the Exchange Control Panel, you can configure this field by selecting a value from 1 to 10 (the default is 3). However, after you create a migration batch but before you start it, you can use Windows PowerShell to increase this number to a maximum of 50 mailboxes to migrate at the same time.

This setting is enforced only during the initial synchronization when you migrate a new batch of mailboxes. It doesn't apply when Exchange Online retrieves new messages sent to users' mailboxes in the on-premises messaging system or when you delete a migration batch.

Important

The Number of mailboxes to migrate simultaneously field specifies the number of connections to your on-premises mail server used during migration. The more connections you have to your on-premises mail server, the more mailboxes you can migrate at one time. While this reduces the amount of time it takes to migrate mailboxes, these additional connections can consume your Internet bandwidth, negatively affecting network performance and users' ability to access Internet resources. For more information, see Maximum Number of Connections to Your Mail Server.

To increase the number of mailboxes that you can migrate at the same time, perform the following steps.

  1. Use the Exchange Control Panel to create a new migration batch.

  2. After the migration batch is created, run the following PowerShell command to increase the number of mailboxes to migrate at the same time.

    Set-MigrationBatch -Identity <migration batch name> -MaxConcurrentMigrations <number>

    For example, to migrate 50 mailboxes at the same time for a migration batch named IMAPBatch1, run the following command.

    Set-MigrationBatch -Identity IMAPBatch1 -MaxConcurrentMigrations 50

    To verify the number of mailboxes to migrate at the same time for a migration batch, run the following command.

    Get-MigrationBatch -Identity <migration batch name> | fl MaxConcurrentMigrations

  3. In the Exchange Control Panel, start the migration batch.