Verifying the same Domain in Separate O365 Tenant

[almarlibetario]

Hello Everyone,

I know this question sounds really dumb but I hope any of you here has the same requirement as me.

The Scenario:

We are about to have an O365 Tenant to Tenant Migration and 1 of the requirement is to sync the on-premise AD users to the new Tenant. Currently, they do not have the synchronization and all email users are purely on cloud and they have a separate account for on-prem login.

I know it is still not supported to verify a domain in multiple O365 tenants but I am just wondering if there is already a workaround for this. In my past experiences, when we tried to sync on-premise users to O365 without a verified domain, they were automatically being assigned an onmicrosoft.com domain. However, when the on-premise domain has been verified in O365, some users UPN did not change automatically. Though the verified domain is still there, it was assigned as Alias not primary.

On this project, we are trying to avoid this scenario as we are dealing with 1000+ users and multiple business entities on a single tenant.

Any inputs are highly appreciated. Thank you and be safe everyone!

[#2]

Add a subdomain, or use the default onmicrosoft.com domain.

[#3]

You cannot do tenant to tenant migration using 365 alone. You need to have a third-party migration application. Because you need to remove the domain from existing tenant to add it to your other tenant so the migration tool keeps your email in their queue until you finish your migration. Please find below link for the trusted third-party tenant to tenant migration partner. 

https://www.quadrotech-it.com/office-365-tenant-to-tenant-migration/

@almarlibetario 

[#4]

@sheahandc yeah, I am using 3rd party migration tool. I just needed to know if there is an option to verify one domain in both O365 tenants.

[#5]

@Vasil Michev Will consider this one. Thanks for your inputs.

[#6]

Answer is you cannot do that.

Please find below link for reference.

https://answers.microsoft.com/en-us/msoffice/forum/all/same-domain-in-two-tenants-is-it-possible-now...

@almarlibetario 

[#7]

@almarlibetario  Hi, you can migrate from one tenant to another using the same domain name. We use a tool that sets up a routing domain to allow this. You can complete the mailbox portion with zero downtime or mail flow interruption. If the migration will be drawn out (not over the weekend) then that's your best bet.  If you can get the migration done over a weekend and can handle down-time then you can use a temporary domain for the transfer. You will need to use a "new" tenant name though, this is unavoidable.