365 Tenant To Tenant Migration

Copper Contributor

I have a tenant who is not set up to be GCC compliant. We have created another tenant that is now GCC compliant and need to move the tenants from the original tenant to the newly created GCC compliant tenancy. I am not sure how we can go about doing this with the destination and origination having the same domain name. I have created the users with the onmicrosoft accounts, instead of the .org users, but we still have the issue of migration. How do we move these users? What is the expected down time for their domain if we use a dummy domain? I am very concerned this is going to result in a massive loss of data.

7 Replies

Hi @Scott_McDonald90 ,


you might want to check tenant-to-tenant migration, Microsoft docs: Microsoft 365 tenant-to-tenant migrations - Microsoft 365 Enterprise | Microsoft Docs


I would also advise to use Third-Party tool like Bittitan - BitTitan MigrationWiz | Migrate to Microsoft 365, Exchange, and G Suite. Bititan will also provide support, but it will cost you 12-15 dollars per user. Depending on what you want to move, just emails or more.





Unfortunately that document does not cover the steps or the details for this type of migration. It does cover tenant to tenant, but does not cover if the migration involves two tenants with the same domain name.

Hi @Scott_McDonald90 ,


these are the seps: Cross-tenant mailbox migration - Microsoft 365 Enterprise | Microsoft Docs


If you have never done migration before, I would recommend that you consult with someone who has done it before. Someone in your area or as I mentioned before, you could do it with a third-party. This process could be complex, and it requires planing. 


Here is the video on how it's done. This is just a small part but just to give you an idea: MigrationWiz for Office 365: Mailboxes - YouTube


Good luck! 

You can perform your migration with a solution like this:
For detaching and reattaching the domain I would suggest to use this feature during the detaching operation

Migrating users between Office 365 tenants with the same domain name presents a challenge, but it can be done with minimal downtime. Here's how to approach it, focusing on minimizing data loss and downtime:

Understanding the Limitation:

Microsoft doesn't allow the same domain to exist in two Office 365 tenants simultaneously. This means you can't directly migrate user mailboxes while keeping the original ".org" addresses.

Solution with Minimal Downtime:

  1. Prepare the Destination Tenant:

    • Ensure the new GCC compliant tenant has user accounts created with temporary onmicrosoft.com addresses.
  2. Prepare the Source Tenant:

    • Don't Delete Users: Avoid deleting users in the original tenant. This preserves their mailbox data.
    • Configure Email Forwarding (Optional): Set up email forwarding in the source tenant to temporarily forward emails to the new onmicrosoft.com addresses in the destination tenant. This minimizes disruption during migration.
  3. Domain Transfer (Short Downtime):

    • Remove the custom domain (".org") from the source tenant. This will cause a brief email outage (usually under an hour).
    • Add the same domain (".org") to the destination tenant.
  4. Mailbox Migration:

    • Use a third-party migration tool designed for Office 365 tenant-to-tenant migration. These tools can migrate user mailboxes, contacts, and calendars. Popular options are  Shoviv Exchange Server Suite, Bittitan, cloudyway, etc.
  5. User Account Updates:

    • Once migration is complete, update user accounts in the destination tenant to use the original ".org" email addresses as their primary aliases.

Data Loss Prevention:

  • Third-party migration tools are generally reliable, but it's crucial to back up data before starting the migration process.
  • Verify the migration is complete by reviewing mailbox content in the destination tenant.

By following these steps, you can migrate your users to the GCC compliant tenant with minimal downtime and data loss.

When it comes to Microsoft 365 (previously Office 365) tenant-to-tenant migrations, there are numerous options available to help. The "best" solution is determined by aspects such as migration complexity, data volume to be transferred, your organization's specialized needs, and budget. The following are some prominent solutions for 365 tenant-to-tenant migration:


Microsoft SharePoint Online Migration Tool: This tool is designed to migrate SharePoint sites, lists, libraries, and content between Microsoft 365 tenants. It supports both SharePoint Online and OneDrive for Business migrations.

Exchange Online PowerShell Commands: Microsoft offers PowerShell scripts and cmdlets to migrate Exchange Online mailboxes and data between tenants. While this method necessitates technical expertise, it might be useful for smaller migrations.

Aryson Exchange Server Backup & Restore Tool: Aryson Exchange Server Backup & Restore Tool provides migration solutions tailored exclusively for Exchange Online migrations, including tenant-to-tenant migrations. Migration Manager for Exchange simplifies migrations while minimizing downtime and data loss.

You can also get expert suggested solution fromhttps://medium.com/@mithileshtata/office-365-tenant-to-tenant-migration-with-ease-ultimate-guide-d51...

Tenant to Tenant Migration can be performed manually. But it now requires cross-tenant user data migration license. Earlier it was not necessary. You can check out the below mentioned guide for complete manual procedure using native method.


Read Here: Perform Office 365 Tenant to Tenant Migration step by step (cloudbik.com)