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Hybrid migration


Hybrid migration is a migration method that integrates an on-premises Exchange environment with Microsoft 365 or Office 365, creating a seamless and feature-rich experience for users and administrators. This approach allows for coexistence between the on-premises Exchange server and Microsoft 365, enabling organizations to gradually migrate mailboxes and maintain some mailboxes on-premises if needed.

Key Features of Hybrid Migration

  1. Coexistence and Integration:

    • Provides a seamless user experience with unified GAL (Global Address List), shared calendars, and free/busy information between on-premises and cloud mailboxes.
    • Supports single sign-on (SSO) for a consistent login experience.
  2. Flexible Migration:

    • Mailboxes can be moved to Microsoft 365 gradually, at your own pace.
    • Suitable for organizations with more than 2,000 mailboxes, but can also be used by smaller organizations needing a prolonged migration period.
  3. Hybrid Configuration:

    • Requires setting up a hybrid configuration using the Hybrid Configuration Wizard (HCW), which assists in configuring and managing the hybrid deployment.
    • Involves setting up a hybrid server to handle secure mail flow between on-premises and Microsoft 365.
  4. Pre-migration Tasks:

    • Verify that your domain is set up and configured correctly in Microsoft 365.
    • Prepare your on-premises Exchange environment, ensuring it meets the requirements for hybrid deployment.
    • Set up and configure Azure AD Connect for directory synchronization.
  5. Migration Process:

    • Use the Hybrid Configuration Wizard to configure the hybrid deployment.
    • Move mailboxes to Microsoft 365 as needed, while keeping others on-premises.
    • Monitor and manage the hybrid environment through the Exchange admin center (EAC) and the Microsoft 365 admin center.
  6. Post-migration Tasks:

    • Assign licenses to users with mailboxes in Microsoft 365.
    • Update DNS records to ensure proper mail flow.
    • Continue to manage both on-premises and cloud mailboxes using hybrid management tools.
    • Decommission the on-premises Exchange server if fully transitioning to Microsoft 365.


  • Seamless Experience: Provides a unified experience for end users, maintaining the look and feel of a single email environment.
  • Flexibility: Allows for a gradual migration of mailboxes, providing flexibility and reducing the risk of disruptions.
  • Advanced Features: Enables advanced features like shared calendar and free/busy information across environments.


  • Complexity: More complex to set up and manage compared to cutover or staged migration.
  • Resource Intensive: Requires maintaining on-premises infrastructure alongside Microsoft 365, potentially increasing management overhead.

Ideal Scenarios for Hybrid Migration

  • Large enterprises with more than 2,000 mailboxes that require a phased migration.
  • Organizations needing to maintain some mailboxes on-premises due to regulatory or business requirements.
  • Companies seeking to provide a seamless, integrated experience between on-premises and cloud environments during the migration period.


Hybrid migration is an ideal solution for large organizations looking to integrate their on-premises Exchange environment with Microsoft 365. It allows for a smooth, gradual transition, offering flexibility and advanced features like unified GAL, shared calendars, and SSO. Although it requires more setup and management compared to other migration methods, the hybrid approach provides a seamless user experience and enables organizations to move mailboxes at their own pace, making it suitable for complex and large-scale migrations.

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