Mastering Cross-Tenant Mailbox Migrations in Mergers, Acquisitions & Rebranding
Cross-tenant mailbox migrations are crucial during business transitions like mergers, acquisitions, and rebranding. They seamlessly transfer user email data between different Microsoft 365 tenants, ensuring business continuity. This guide equips you with the knowledge to navigate this process effectively.
Understanding Cross-Tenant Mailbox Migrations
Cross-tenant migrations move user mailboxes (emails, contacts, calendars) across different Microsoft 365 tenants. This ensures users retain access to their critical information during organizational changes.
Benefits of Cross-Tenant Migrations:
Streamlined Workflow: Maintain user productivity by migrating email data between tenants.
Business Continuity: Minimize disruption during M&A or rebranding efforts.
Centralized Management: Consolidate user data in a single tenant for easier administration.
Actionable Steps for Cross-Tenant Migration:
Define Scope and Users: Identify user base and data volume to be migrated.
Prepare Source and Target Tenants: Ensure licensing, permissions, and domain names are properly configured.
Initiate Migration Process: Utilize Microsoft tools or third-party migration solutions.
Post-Migration Tasks: Reassign permissions, update meeting URLs, and address mailbox conversion in the source tenant.
What Gets Migrated (and What Doesn't)
Migrated Content:
User emails, contacts, calendar entries, tasks, and notes
Recoverable Items folders (limited to deletions, versions, and purges)
Non-Migrated Content:
Non-user-visible items like Teams chat data (requires additional steps)
Post-migration changes like meeting URLs require user updates
Permissions (like Send On Behalf Of) need to be reassigned in the target tenant
Additional Considerations
Category | Details |
Domain Names | Source and target tenant domain names must be unique (e.g., "contoso.com" can't be added to the target tenant while still in use by the source tenant). Beware of NotAcceptedDomain errors during migration. |
Labels and Groups | Labels do not sync or transfer between tenants. After migration, you'll need to recreate the labels in the target tenant. Also, Microsoft 365 Group and public folder mailboxes cannot be migrated. |
eDiscovery | Post-migration, eDiscovery against the migrated user's mailbox in the source tenant is not possible. Consider copying the mailbox contents to a second mailbox before migrating for future eDiscovery needs. |
Auxiliary Archive MBX | The migration process supports moving users with up to 12 auxiliary archive mailboxes. Migration will fail if a user has more than 12 auxiliary archive mailboxes. |
Conclusion:
Cross-tenant mailbox migrations require careful planning and execution. By understanding the capabilities, limitations, and essential steps involved, you can ensure a smooth transition and minimize disruption during business transformations.
Need expert assistance with your cross-tenant mailbox migration? Contact us today for a free consultation!
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