Migration from Exchange to Exchange Online Tenant to Tenant

Moving to the cloud is a significant step for any organization. When it comes to email, migrating from an on-premises Exchange server to Exchange Online in a different tenant presents unique challenges. This article provides a comprehensive guide for a smooth tenant-to-tenant mailbox migration, outlining the process, key considerations, and best practices.

Understanding the Scenario

This migration involves moving mailboxes from an on-premises Exchange environment to Exchange Online within a different Office 365 tenant. This is common in scenarios like mergers, acquisitions, or divestitures where organizational restructuring necessitates shifting users and their data to a new tenant.

Top Method to Perform Tenant-to-Tenant Migration

Users have two primary options for mailbox migration: migrating from Exchange to Exchange, or from Exchange to Exchange Online (Office 365). The first option is a manaul method requiring some technical expertise, while the second involves using automated third-party tool. Ultimately, the choice of which method to use depends on the user’s specific needs and preferences. This article will focus on the manaul method—let’s begin!

Prerequisites

Before initiating the migration, ensure you have:

• Sufficient licenses: Verify you have the necessary Exchange Online licenses in the target tenant for all migrating users.
• Administrative access: Obtain appropriate administrative credentials for both the source (on-premises Exchange) and target (Exchange Online) tenants.
• Network connectivity: Establish a reliable and secure network connection between your on-premises environment and Exchange Online.
• Directory synchronization: Set up directory synchronization (Azure AD Connect) to synchronize user accounts between your on-premises Active Directory and the target Azure Active Directory.
• Organization relationship: Configure an organization relationship between the source and target tenants. This allows for cross-tenant mailbox moves using Exchange Online PowerShell.

Migration Process

1. Assessment and Planning:

   • Inventory mailboxes: Identify the mailboxes to be migrated and gather information about their size, content, and user requirements.
   • Plan the migration timeline: Determine the migration window and schedule downtime if necessary.
   • Communicate with users: Inform users about the migration process, timeline, and potential impact.

2. Prepare the Source Environment:

   • Verify mailbox health: Ensure mailboxes are healthy and errorsfree before migration.
   • Upgrade Exchange Server: If necessary, upgrade your on-premises Exchange Server to a supported version for hybrid connectivity.
   • Configure hybrid connectivity: Establish hybrid connectivity between your on-premises Exchange organization and Exchange Online.

3. Prepare the Target Environment:

   • Create user accounts: Ensure corresponding user accounts exist in the target tenant’s Active Directory.
   • Assign licenses: Assign the appropriate Exchange Online licenses to the user accounts.
   • Configure necessary settings: Configure any required settings in the target tenant, such as email address policies and retention policies.

4. Mailbox Migration:

   • Use cross-tenant mailbox migration: Leverage the New-MigrationBatch cmdlet in Exchange Online PowerShell to perform the mailbox moves.
   • Monitor the migration progress: Track the status of the migration batches and address any errors or issues.
   • Validate mailbox functionality: After migration, verify that users can access their mailboxes and all email functionality is working as expected.

5. Post-Migration Activities:

   • Decommission on-premises Exchange: Once all mailboxes are migrated and validated, decommission your on-premises Exchange servers.
   • Update DNS records: Update your MX records to point to Exchange Online.
   • Provide user support: Offer ongoing support to users as they adjust to the new environment.

Best Practices

• Test the migration process: Perform a pilot migration with a small group of users before migrating all mailboxes.
• Use migration tools: Consider using third-party migration tools to simplify the process and automate tasks.
• Throttle migration traffic: To minimize impact on network performance, throttle the migration traffic during peak hours.
• Maintain detailed documentation: Document the migration process, including any issues encountered and resolutions implemented.

References:

1. Exchange Migration tool
2. Exchange to Office 365 Migration tool
3. Migrate from Exchange to Office 365
4. Office 365 Tenant to Tenant Migration Step by Step
5. Migrate Exchange to Exchange Online
6. Exchange Recovery
7. Migrate Exchange 2016 to Office 365

Conclusion

Migrating mailboxes from an on-premises Exchange environment to Exchange Online in a different tenant requires careful planning and execution. By following the outlined steps, leveraging appropriate tools, and adhering to best practices, you can ensure a smooth and successful migration, minimizing disruption to your organization’s email operations.