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Staged migration


Staged migration is another method for migrating email from an on-premises Exchange server to Microsoft 365 or Office 365. Unlike cutover migration, staged migration is designed for larger organizations that need a phased approach to migration. This method is particularly useful when an organization has more than 2,000 mailboxes and prefers to move them in batches over a period of time.

Key Features of Staged Migration

  1. Phased Approach:

    • Mailboxes are migrated in batches, allowing for a more controlled and manageable transition.
    • Suitable for organizations with more than 150 mailboxes and up to 2,000 mailboxes.
  2. Migration Process:

    • Migrates only user mailboxes. Other components like distribution groups and contacts must be manually recreated or migrated separately.
    • Involves synchronizing on-premises and cloud mailboxes until the migration is complete.
  3. Pre-migration Tasks:

    • Verify your domain is set up in Microsoft 365.
    • Ensure your on-premises Exchange environment is ready for migration.
    • Prepare the on-premises Active Directory and ensure it’s synchronized with Microsoft 365 using Azure AD Connect.
  4. Migration Process:

    • Configure Exchange Web Services (EWS) on your on-premises Exchange server.
    • Create and configure a migration endpoint in Microsoft 365.
    • Create migration batches to move mailboxes in stages. Each batch can include up to 1,000 mailboxes.
    • Monitor and manage each migration batch through the Exchange admin center (EAC) in Microsoft 365.
  5. Post-migration Tasks:

    • Assign Microsoft 365 licenses to users whose mailboxes have been migrated.
    • Update DNS records to point to Microsoft 365 for mail flow.
    • Ensure users' Outlook profiles are reconfigured to connect to Microsoft 365.
    • Migrate additional components like distribution groups and contacts if necessary.
    • Optionally, decommission the on-premises Exchange server once all mailboxes are migrated and mail flow is confirmed.


  • Controlled Transition: By migrating in stages, organizations can better manage the migration process, minimizing disruption to users.
  • Flexibility: Allows for testing and adjustment between batches, ensuring a smoother overall migration.
  • Lower Initial Impact: Reduces the immediate workload on IT staff compared to migrating all mailboxes at once.


  • Complexity: More complex than cutover migration due to the need to manage multiple batches and synchronization processes.
  • Longer Migration Time: Takes more time to complete as it involves multiple stages.

Ideal Scenarios for Staged Migration

  • Organizations with a large number of mailboxes (between 150 and 2,000) that need to be moved to Microsoft 365.
  • Businesses that require a phased approach to reduce potential disruptions and better manage the migration process.
  • Companies that need to maintain coexistence between the on-premises Exchange server and Microsoft 365 during the migration period.


Staged migration is an effective method for larger organizations needing a controlled and phased transition to Microsoft 365. By moving mailboxes in batches, staged migration reduces the complexity and disruption of the migration process, allowing IT departments to manage the transition more effectively. This method ensures that organizations can gradually move their email infrastructure to the cloud while maintaining day-to-day operations.

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