M365 - tenant to tenant migration with 2way cross forest trust

Trevor 66 Reputation points

Hi guys,

I need your practical guidances how to properly plan to divide and migrate part of users from tenant A and move them to tenant B using 2way AD trust. This concers especially Microsoft Online mailboxes as well as Teams, Onedrive.

So, currently company A has hybrid environment, so local AD which i synchronized with O365 tenant. Our plan is to setup new hybrid Active Directory with new Azure and M365tenant B.
Then we'll establish 2way trust with company A in order to synchronize users using ADMT.

Now based on article ( https://learn.microsoft.com/en-us/microsoft-365/enterprise/cross-tenant-mailbox-migration?view=o365-worldwide) how we could match/migrate mailboxes between the tenants with usage of existing synchronized identities??

In the above article there is a requirement, as below:

"Users migrating must be present in the target tenant and Exchange Online system (as MailUsers) marked with specific attributes to enable the cross-tenant moves. The system will fail moves for users that aren't properly set up in the target tenant. The following section details the MailUser object requirements for the target tenant."

Can I assume that it we will syc users between tenants, then in new tenant B we will setup for synced users new UPN, we can match required attributes and migrate mailboxes ?? Does this requirement mentioned in the MS article will be filled ?

Active Directory
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A set of directory-based technologies included in Windows Server.
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Azure Active Directory
An Azure enterprise identity service that provides single sign-on and multi-factor authentication.
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  1. Rached Chader 231 Reputation points


    generally for this kind of migration I go through BitTitan it's easier.

    Good luck

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