Hi all, I have a question with regards to an Office 365 Tenant to Tenant migration that I hope someone can help me. As an example, the source tenant is fabrikam.com, and the destination is contoso.com and what I have done to prepare for the migration is I have added fabrikam.com as a domain in local AD for contoso.com so that I can create pre-create the user accounts and set their UPN to fabrikam.com. The users have been synced to the destination tenant, and they are obviously being assigned a contoso.onfabrics.com address as the UPN as the fabrikam.com domain does not exist yet in the contoso.com tenant.
So my question is when the domain is finally cutover to the contoso.com tenant, will the user accounts automatically update their UPN to fabrikam.com? Or would it be better to set the accounts UPN to a non-routable domain, and then...