Cross-Tenant Migration In Office 365: What It Is
And How To Do It Right


In the rapidly evolving landscape of modern business, companies are constantly engaging in mergers, acquiring other firms, or undergoing restructuring. Consequently, IT departments frequently encounter the task of transferring resources between different Office 365 tenants, a procedure referred to as cross-tenant migration. Although Office 365 (currently integrated into Microsoft 365) provides robust tools for enhancing collaboration and productivity, the process of transferring data between tenants is not merely a straightforward copy-and-paste operation. It requires meticulous planning, specialized technical skills, and an effective strategy to prevent any interruptions. Check out the DuoCircle for gaining further insight.


What Is Cross-Tenant Migration?


Cross-tenant migration refers to the process of transferring Office 365 assets—such as email accounts, OneDrive documents, SharePoint sites, Teams information, and more—from one organizational tenant to another. Each tenant functions as a distinct instance of Microsoft 365, complete with its security settings, user identities, licenses, and configurations.

This type of migration is frequently seen in situations such as the following:

  • Mergers and acquisitions: When two companies merge, they often need to unify their IT systems.

  • Divestitures: When a company separates from a business division, it necessitates the creation of an independent Office 365 environment.

  • Brand restructuring: Organizations may undergo internal changes that require new domain names and tenant arrangements.

In contrast to conventional on-premises migrations, moving resources between tenants in Office 365 can present greater challenges due to variations in authentication methods, licensing agreements, and system architecture.



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Key Challenges of Cross-Tenant Migration


Transitioning between tenants comes with its own set of obstacles. Below are some of the major difficulties encountered by IT teams:


Identity and Authentication

Every tenant operates with its instance of Azure Active Directory (Azure AD). When migrating users, it is crucial to manage identity data meticulously to guarantee that individuals can continue to log in without interruption following the transition. You must determine whether to combine directories, synchronize identities, or transition to a different directory service.


Data Integrity and Compliance

Ensuring the accuracy and consistency of data during migration is essential. Organizations need to safeguard against any loss or corruption of emails, documents, or chat records. Additionally, there may be stringent compliance obligations that need to be met, particularly in sectors such as healthcare and finance that are heavily regulated.


Downtime Minimization

Companies cannot sustain extended periods of inactivity. Careful planning for migration helps reduce service disruptions and keeps employees engaged and efficient throughout the changeover.


Licensing and Subscriptions

After migration, users in the new tenant must be assigned the correct Microsoft 365 licenses. Failing to do so may lead to losing access to vital services such as Exchange Online or Teams.


How to Execute a Successful Cross-Tenant Migration


To successfully execute a smooth migration between tenants, it's essential to follow a well-organized strategy. Below is a general outline of the key steps involved:


1. Assessment and Planning

Begin with a thorough evaluation of the source and destination tenants. Determine the following:

  • The total count of users, mailboxes, and workloads (such as Exchange, OneDrive, SharePoint, Teams, etc.)

  • Any custom domains currently utilized

  • Security and compliance necessities

  • Licensing factors to consider

Develop a comprehensive migration strategy that outlines timelines, methods of communication, and backup plans in case of rollback.



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2. Pre-Migration Activities

Before initiating the migration:

  • Inform users regarding the forthcoming modifications and what they should anticipate.

  • Streamline the source tenant by eliminating outdated accounts, archiving historical data, and addressing any current problems.

  • Set up the target tenant by configuring domains, licenses, policies, and settings.

  • If required, create a trust relationship between Azure AD directories to facilitate smoother authentication.

3. Migration Execution

Based on the type of data you are transferring, you have the option to utilize built-in tools (such as Microsoft's latest tenant-to-tenant migration capabilities) or opt for external services like BitTitan, Quest, or AvePoint.

Important factors to keep in mind during this stage include:

  • Ensuring a smooth mailbox migration with little interruption

  • Transferring files from OneDrive and SharePoint

  • Migrating Teams information, including chat histories, channels, and tabs

  • Actively tracking the migration progress to identify and address any potential problems promptly.

4. Post-Migration Steps

Following the migration:

  • Ensure that all data has been successfully migrated.

  • Distribute licenses as needed.

  • Modify DNS records to direct traffic to the new tenant.

  • Perform user acceptance testing.

Offer assistance to users with any issues or training requirements that arise after the migration.