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Source Mailbox Status After Microsoft 365 Cross-Tenant Migration
Question details
The user wants to know the status of source mailboxes post-migration and if it is possible to keep them available in both source and destination tenants.
- Product
- Microsoft 365
- Device & OS
- not provided
- Scenario
- Migrating mailboxes between Microsoft 365 tenants.
- Observed behavior
- The user aims to maintain active and accessible mailboxes in both the source and destination Microsoft 365 tenants simultaneously.
Before initiating a cross-tenant migration, ensure you have verified your destination tenant's storage capacity and communicated the expected cutover time to your users.
Understand Standard Cross-Tenant Migration Behavior
Review what happens to your source mailbox by default when using Microsoft's native cross-tenant migration process.
During a standard cross-tenant mailbox migration, all user-visible content including emails, contacts, calendars, tasks, and notes is transferred to the destination tenant. Once the migration successfully completes, Microsoft automatically deletes the source mailbox. It will no longer be available, discoverable, or accessible in the original tenant.
Log into the destination Microsoft 365 tenant to ensure all emails, contacts, and calendar events have successfully synced.
Access the source Microsoft 365 Exchange admin center to verify that the original mailbox has been removed as per the standard migration cutover process.
Implement a Coexistence Strategy Using Third-Party Tools
Use alternative methods if your organization requires mailboxes to remain available in both the source and destination tenants.
Boost Your Productivity with WPS Office
While managing complex Microsoft 365 tenant migrations, you still need a reliable suite for your daily document tasks. WPS Office provides a free, lightweight, and highly compatible alternative to Microsoft Office, ensuring smooth document creation and editing without heavy subscription fees.
- 1. Download the installer: Visit the official WPS Office website and download the free installation package for your Windows, Mac, or Linux operating system.
- 2. Install WPS Office: Run the downloaded installer and follow the simple on-screen instructions to set up the software on your computer.
- 3. Open existing documents: Launch WPS Office and open your existing Microsoft Office files directly to enjoy full format compatibility and familiar editing tools.
Frequently Asked Questions
Can I recover a source mailbox after a cross-tenant migration?
In a standard native migration, the source mailbox is deleted upon completion. However, depending on your retention policies, the deleted mailbox data might be retained in the source tenant as a soft-deleted mailbox for a standard period (typically 30 days), during which an administrator can recover it.
Does a cross-tenant migration move my OneDrive files as well?
A standard cross-tenant mailbox migration specifically handles email, contacts, calendars, tasks, and notes. Moving OneDrive files and SharePoint data requires a separate migration process or specialized third-party tools.
Will end users notice when their source mailbox is deleted?
Yes, once the migration is finalized and the source mailbox is deleted, users will no longer be able to access the old tenant's mailbox. Administrators should prompt users to restart Outlook and reconfigure their profiles to connect to the new destination tenant.
