On-prem/365 Domain Mismatch: Is it possible to migrate to a tenant from a different domain?

Question

Hi,

I am preparing to migrate our org to full 365 from a full on-prem environment. The issue I have is that our on-prem AD DS domain is not owned by us and cannot be used as the tenant or as a verified domain in 365. For example: on-prem is contoso.com, 365 tenant is microsoft.com. Our users are contoso\user accounts with user@microsoft.com email addresses.

My questions are:

Will AAD Connect function in a hybrid mode between different domains so we can import users into Entra under the correct domain?

If this isn't possible, which I suspect it's not, will there be any issues importing a pst into Exchange Online of a "microsoft.com" (tenant matching) mailbox export?

The users will be able to handle not having their profiles, but their mailboxes are another issue.

Thanks in advance.

Answer 1

Hi, @Anthony Turner

Since I focus on Exchange Online, I know very little about AAD, as far as I know, Azure AD Connect typically requires that the local domain be validated in Azure AD. Since you mentioned that your local domain is not owned by you and cannot be used as a verified domain in a 365 tenant, it may not be straightforward to use AAD Connect in traditional hybrid mode with two different domains.

Importing a PST file into Exchange Online should not present any significant issues. For more information on how to import a pst file check out. Learn about importing organization PST files | Microsoft Learn

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