Tenant to tenant migration

Question

We completed tenant (source) m365 Domain A to tenant (destination) m365 Domain B migration.

Migrated Users using domain B accounts and wish to continue receive emails from Domain A accounts.

Tasks:1

1.Now we are looking to detach domain A from source Tenant and add domain A to destination M365 side.

2.Complete shutdown source M365 Tenant.

Task:2

Create Aliases for Domain A to continue receive emails.

Please help with steps?

Answer 1

Hi @ TA.Saurabh.Singh，

From your plan description, we know that all users have been moved out of your source organization. The next step should be to check and update the source tenant's DNS records so that you can remove it from the source tenant.

For detailed steps, you can refer to the steps in the official document:

1. Remove domain A: from the source tenant： Remove a domain - Microsoft 365 admin | Microsoft Learn
2. Add domain A to the target tenant: Add a domain to Microsoft 365 - Microsoft 365 admin | Microsoft Learn
3. Delete the source tenant: Delete an Azure Active Directory tenant - Microsoft Entra | Microsoft Learn
4. Create aliases for a mailbox in the new tenant: Add another email alias for a user - Microsoft 365 admin | Microsoft Learn

In addition, due to the lack of email address policies in Exchange online, you need to update users' email addresses in bulk through a PowerShell script:

Bulk Add SMTP Addresses to Office 365 Mailboxes (practical365.com) 

(Note:Microsoft provides third-party contact information to help you find additional information about this topic. This contact information may change without notice. Microsoft does not guarantee the accuracy of third-party contact information.）

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