Migrating multiple different tenants to one new tenant

Question

Hi,

We are merging our three different barnches into one common tenant. This is a new tenant which at the moment is empty.
Two of them are hybrid on-prem and azure tenants, and the last one is Azure only. A total of around 100 user accounts.
We need to get all users,emails, Teams and SharePoint sites to the same tenant. Users will receive a new email adress, but must be able to use todays email addresses too.

What is the best practice to do this?
I was thinking of doing a Cutover Exchange Migration for the emails. But can this be done for the branch that is Azure only already?
Also thinking of pointing the AD sync tool to the new tenant, but is there a way to migrate the existing Azure tenants to the new tenant?

Maybe some other path would be better, so please point me in the right direction.

Regards,

Answer 1

@Arve ,

As far as I know, Cutover Exchange migration is for on-premises to Office 365 migrations, not online to online migrations.

For Cross-tenant mailbox migration, please refer to:

https://learn.microsoft.com/en-us/microsoft-365/enterprise/cross-tenant-mailbox-migration?view=o365-worldwide

Cross-tenant Exchange mailbox migrations are supported for tenants in hybrid or cloud only, or any combination of the two.

In addition, please check out the guidance on Microsoft 365 tenant-to-tenant migration in this article:

https://learn.microsoft.com/en-us/microsoft-365/enterprise/microsoft-365-tenant-to-tenant-migrations?view=o365-worldwide

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Answer 2

Hi @Arve

I understand that you are looking to merge three tenants into one, and that two of these tenants are hybrid tenants and one is Azure-only.

You will need to manually add the new user objects in the Azure AD and provide the necessary permissions. There is no out-of-the box tool in Azure or Microsoft 365 that does this, so you will either need to re-create the users and resources.

Merging tenants is a relatively complex task and it is difficult to provide precise guidance for this, especially if you have larger tenants or have services outside of Azure AD such as Sharepoint and mailboxes. You can move entire subscriptions between tenants, but if you do that you will lose all of your RBAC assignments and not every resource can handle something like that. You will most likely need to recreate many of your resources.

Depending on your needs, you can also look into Azure Lighthouse, which enables logical projection of resources from one tenant to another tenant. It does not, however, physically move data or resources.

Another option would be to use the ADMT migration tool to consolidate the on-premises Active Directories and then synchronize them.

Additional resources:
Cross-tenant management experiences
Merge/move two ADs and one Office 365 tenant to a new AD

Marilee