Merging of companies best practice?

Question

Hello there,

we currently have Active Directory on premise which is synchronizing its objects to a Azure AD with AAD Connect. We
have acquired a new company with its own Azure AD Domain and they do not have a premise AD. What will be the best way to migrate
them to our domain?

Thanks in advance

Answer 1

@Hristo Hristov

Thank you for posting your query in Microsoft Q&A.

Let's say you have tenant A where users are synced from on-premises to tenant A using AD connect.
You have newly acquired new company who has users in Tenant B and they do not have any on-premises environment.

You will have to first verify Tenant B domain in your Tenant A. For this you will have to remove the domain from Azure AD of Tenant B and then you will be able to verify this domain in your Tenant A.

Post this you will have to create all the users in Tenant A that you had earlier in Tenant B.
After doing this you can assign licenses to users accordingly as per your requirement.

If users had mailboxes online previously in tenant B then you can follow below article to migrate mailboxes to Tenant A.
https://learn.microsoft.com/en-us/exchange/mailbox-migration/migrate-mailboxes-across-tenants?source=recommendations

Let me know if you have any questions.

Please "Accept the answer" if the information helped you. This will help us and others in the community as well.

Answer 2

Configure company B as an internal relay domain in company A, en configure a send connector for the respective domains pointing to company B endpoints. If you have mail-users post-migration in company B (eg, mailboxes moved from company B to company A), make sure you set targetAddress to a domain uniquely defined in company A(e.g., when rebranding set to company Aaddress). This prevents you from having 2 locations with disjoint populations requiring internal relays for that domain pointing to each other (with bouncing NDRs). Alternatively, introduce a mail routing domain - similar to Office 365 - such as mail.compb.com, which is an accepted domain in company A, the internal relay in company B, and set targetAddress in company B to those entries.