Adding domain to Azure AD from a different tenant

Question

Currently we have a tenant for all staff. A previous director setup a separate tenant for students. I would like to pull one domain (ex: students.company.com) from another tenant (default domain) to our tenant (ex. company.com). Can I delete the other domain from the tenant and add it to ours? What would be lost on the delete and add? Some student use the other domain as license for office. I can give them a license under the new tenant.

Answer 1

Hello Ron,

I'd recommend checking out this page (with PDF) for the checklist:

Microsoft 365 tenant-to-tenant migrations

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

Here is a guide if you want to move mailboxes (you can use Microsoft or a third-party tool to move the mailboxes):

How to migrate mailboxes from one Microsoft 365 or Office 365 organization to another

https://learn.microsoft.com/en-us/Exchange/mailbox-migration/migrate-mailboxes-across-tenants

Also, you should be thinking do you have any data or SharePoint on the one tenant you intend on migrating. Do you intend on migrating this data?

Realistically speaking, if you don't want to migrate anything, remove the domain and then add it:

Remove a domain

https://learn.microsoft.com/en-us/microsoft-365/admin/get-help-with-domains/remove-a-domain?view=o365-worldwide

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Answer 2

@Magers, Ron

Thank you for your post and updates!

I understand that when you removed the users from the domain on the other tenant and added the domain to your current tenant, email stopped sending from your domain to the student domain. To hopefully help point you in the right direction or resolve your issue, I'll share my findings below.

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Findings:

When it comes to the DNS MX records, I noticed that you didn't set that up because the students don't use it for any emails. However, one possibility as to why the emails stopped could be because when you removed the domain from the old tenant and added it to the new tenant, the MX records for the domain weren't updated to point to the correct email service provider.

To resolve this, you'll need to update the MX records for the domain to point to the correct email service provider. In this case, since the student domain is using GSuite, you'll need to update the MX records for the domain to point to Google's email servers.

For more info - Change your domain nameserver records (if needed)

If you set up a custom domain, you added DNS records so the domain would work with Microsoft 365 services. Before you remove your domain, be sure to update the DNS records, such as your domain MX record, at your DNS host. For example, change the MX record at your DNS host. Email sent to your domain stops coming to your Microsoft address and goes to your new email provider instead. (An MX record determines where email for your domain is sent.)

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Additional Links:

• Preparation and pre-migration activities: Three days before you migrate
• Mail exchanger record (MX record) time to live (TTL) test
• MX record change - Stop inbound mail flow

I hope this helps!

If you have any other questions, please let me know. Thank you for your time and patience throughout this issue.

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