First published at https://nivleshc.wordpress.com

There are times when companies acquire other companies to increase their portfolio. When this happens, the acquired company’s IT infrastructure normally gets merged with the parent company. The opposite of this situation is also true. There are also times when a company sells off one of its acquired companies or divisions. In this scenario, the company that is being sold off must have all its IT infrastructure separated from the parent company.

In this blog I will show the steps that can be used to separate a previously acquired company’s email system from its parent company, after the child company has been sold off.

Background

To provide some context, let me provide some details for the parent company and the child company that is being sold off

  • The parent company is called Tail Spin Toys and owns the domain name tailspintoys.com
  • Tail Spin Toys have their own Active Directory Forest called tailspintoys.com and this is synchronised to Azure Active Directory using Azure Active Directory Connect (AADC) server.
  • Tail Spin Toys has a hybrid Exchange Online setup. Their Office 365 tenant is called tailspintoys and has the tenant address of tailspintoys.onmicrosoft.com
  • Tail Spin Toys users have their userprincipalname and primary email address in the form of firstname.lastname@tailspintoys.com
  • The previously acquired company (referred to as child company in this blog) is trading as Wing Tip Toys and owns the domain name wingtiptoys.com. This domain has been added to Tail Spin Toys Office 365 tenant as an additional domain.
  • Wing Tip Toys have their own Active Directory Forest called wingtiptoys.net and all their users, computers and servers are part of this Active Directory Forest.
  • Wing Tip Toys users have their mailboxes provisioned in Tail Spin Toys Office 365 tenant (the process will be explained in the next bullet point). Wing Tip Toys only use email services in Office 365.
  • Each Wing Tip Toys user has two identities. The first is in the wingtiptoys.net Active Directory Domain, which is used to login to their computers and to access their local resources (fileshares, printers etc).
  • The other identity is a user object created in Tail Spin Toys Active Directory Domain. This is used to provision a mailbox in Tail Spin Toys Office 365 tenant. Unfortunately, for Wing Tip Toys users, their Office 365 experience is not very elegant since their userprincipalname for Office 365 is of the form firstname.lastname@tailspintoys.com but their primary email address is of the form firstname.lastname@wingtiptoys.com. The users login to their computers using the wingtiptoys.net samaccountname. However, all users are aware of this and it doesn’t affect them too much.
  • To ensure users are not burdened with having to manage both the user object passwords, Password Change Notification System has been implemented. This replicates any password changes in the wingtiptoys.net Active Directory domain to the respective user object in tailspintoys.com Active Directory domain.

Requirement

Now that Wing Tip Toys has been sold off, all of its data must be separated from Tail Spin Toys. The following will be done for its emails.

  • A new Office 365 tenant will be provisioned for Wing Tip Toys
  • All mailbox data will be migrated to the new Office 365 tenant
  • Once all mailbox data has been migrated, after a few weeks, the Wing Tip Toys mailboxes in Tail Spin Toys Office 365 tenant will be disabled (or deleted)

Migration Plan

Ok, lets get started.

  • Due to the small size of Wing Tip Toys, it has been decided to use a Cloud-Only Office 365 Deployment. ( details on how to configure a Cloud-Only Office 365 deployment can be found here ) however a hybrid Exchange Online environment will still work with the following steps ( a few extra steps will have to be added)
  • BitTitan MigrationWiz will be used to copy the mailbox data from Tail Spin Toys Office 365 tenant to Wing Tip Toys Office 365 tenant

Here are the steps

  1. Add an additional UPN suffix (wingtiptoys.com) to the Wing Tip Toys Active Directory Domain
  2. Configure all Wing Tip Toys users in the wingtiptoys.net domain to have a userprincipalname of the form firstname.lastname@wingtiptoys.com
  3. For all the Wing Tip Toys users in the Tail Spin Toys Office 365 tenant, export their email addresses (we are after the proxyaddresses). Ensure the X500 addresses are also exported.
  4. In the wingtiptoys.net Active Directory domain, for each user, find their email addresses from the export that was done in step 3 and import it into the proxyaddresses attribute of their Active Directory user object. Ensure only email addresses for the domain wingtiptoys.com are imported (if you import any email address for which the domain hasn’t been added to wingtiptoys Office 365 tenant, these will display as the default Office 365 tenant address [@wingtiptoys.onmicrosoft.com] instead of the actual email address). Also, make sure the X500: addresses are also imported. Check to ensure the proxyaddress firstname.lastname@wingtiptoys.com is prefixed with an uppercase SMTP:. This will make it the primary smtp address
  5. Create a new Office 365 tenant for Wing Tip Toys. For simplicity, we will assume that the tenant name is wingtiptoys and the tenant address is wingtiptoys.onmicrosoft.com. Since the domain wingtiptoys.com is already attached to the Tail Spin Toys Office 365 tenant, we won’t be able to attach it to the new tenant just yet.
  6. Install Azure Active Directory Connect (AADC) Server and configure it to synchronise objects from the wingtiptoys.net Active Directory domain to the Wing Tip Toys Azure AD. For Single Sign On, we will enable AADC server for password hash synchronisation however Active Directory Federation Services (ADFS) servers can also be used.
  7. If required, configure the transport rules in Wing Tip Toys Office 365 tenant to match those in Tail Spin Toys Office 365 tenant. For example, to apply disclaimers to all outgoing emails.
  8. Export configuration of all Distribution groups in Tail Spin Toys Office 365 tenant that belong to Wing Tip Toys.
  9. Create a user in Tail Spin Toys Office 365 tenant with the upn migrationwiz@tailspintoys.onmicrosoft.com. For all Wing Tip Toys mailboxes in Tail Spin Toys Office 365 tenant, give migrationwiz@tailspintoys.onmicrosoft.com full mailbox access. This account will be used by Bittitan MigrationWiz.
  10. Create a user in Wing Tip Toys Office 365 tenant with the upn migrationwiz@wingtiptoys.onmicrosoft.com and give it Global Administrator access. This account will be used by Bittitan MigrationWiz.
  11. Provision Office 365 licenses (at least Exchange Online Plan 2) to all user objects in Wing Tip Toys Office 365 tenant that have been synchronised from the on-premise Active Directory domain. This will create mailboxes for them. At this stage, they will only have the email address firstname.lastname@wingtiptoys.onmicrosoft.com (this is because the domain wingtiptoys.com hasn’t been added to this tenant).
  12. Create an account at Bittitan and purchase licenses for MigrationWiz. One license is required for one mailbox data migration, so purchase the required number of licenses ( when you create an account, you are provided with 3 trial licenses. You can use these to test out the migration process).
  13. Use the steps listed at https://help.bittitan.com/hc/en-us/articles/115008106827-Office-365-to-Office-365-Migration-Guide-While-Keeping-the-Same-Domain-Name to configure Bittitan MigrationWiz. The source and destination mailboxes within MigrationWiz must be specified using the Office 365 tenant address, for example in our case, the source mailboxes will be firstname.lastname@tailspintoys.onmicrosoft.com and the destination mailboxes will be firstname.lastname@wingtiptoys.onmicrosoft.com
  14. Pre-Stage the mailbox data for the Wing Tip Toys mailboxes by using MigrationWiz to copy everything except the last 20 days of data from the Tail Spin Toys Office 365 tenant to the Wing Tip Toys Office 365 tenant mailboxes (the more data you pre-stage, the faster the cut-over will be).
  15. Add wingtiptoys.com domain to the Wing Tip Toys Office 365 tenant. You will get a TXT record, which must be used to create a DNS entry in wingtiptoys.com domain, to prove domain owership. Create the DNS record and have the TTL set to 300s (5min). You won’t be able to verify the domain in Wing Tip Toys Office 365 tenant as it is currently attached to the Tail Spin Toys Office 365 tenant.
  16. Change the TTL for the MX DNS entry for wingtiptoys.com to 300s (5min). Make a note of the existing MX entries.
  17. At this stage, all the preparation has been done and we are ready for the cut-over. I would suggest planning the cutover out of office hours, preferably on a Friday evening. Send out user communications at least a week prior to cut-over so that everyone is aware of the change. In the communications, ensure you state that users will not be able to receive new emails in their Mobile and Outlook clients until it has been reconfigured to use the new Office 365 tenant. Provide instructions on how users can reconfigure their Outlook and Mobile clients and also provide the Outlook Web App address (this would be similar to https://outlook.office.com/wingtiptoys.com/ )
  18. Twenty minutes prior to cut-over time, change the MX for wingtiptoys.com to invalid.outlook.com. Setting the MX record to an invalid domain just ahead of the migration causes the sender’s email server to queue the emails and retry later. This will reduce the possibility of Office 365 sending a “recipient not found” Non Delivery Receipt if the email is received for a Wing Tip Toys user after the wingtiptoys.com domain has been removed from the Tail Spin Toys Office 365 tenant but hasn’t been added to the Wing Tip Toys Office 365 tenant.
  19. At cut-over time, remove the domain wingtiptoys.com from Tail Spin Toys Office 365 tenant. A message will be displayed stating that user logins and email addresses will need to be reconfigured. It will also state that the automatic domain removal process will change them to the default domain (tailspintoys.com) and that they will no longer receive emails at wingtiptoys.com. Click Remove. The time taken to remove the domain depends on the amount of mailboxes that have to be reconfigured to use the tenant email address.
  20. Add wingtiptoys.com to the Wing Tip Toys Office 365 tenant. If you receive an error stating that the domain is already attached to another Office 365 tenant, wait for a few minutes and then try again.
  21. Run a Full Synchronisation using Azure Active Directory Connect server and wait for it to complete. Confirm that the userprincipalname and primary smtp address for the users in Wing Tip Toys Office 365 tenant has now changed to the format firstname.lastname@wingtiptoys.com.
  22. Change the MX for wingtiptoys.com to the value shown in the Wing Tip Toys Office 365 Portal under Domain Settings.
  23. Run a full migration using MigrationWiz so that the remaining mailbox data is copied across.
  24. Create a DNS entry in the internal and external DNS server for autodiscover.wingtiptoys.com. The value for this is shown in the Wing Tip Toys Office 365 Portal, under the Domains section.
  25. Test the following scenarios
    • you can login using Outlook Web App to a mailbox in the Wing Tip Toys Office 365 tenant and access all emails.
    • you can configure Outlook client and a Mobile email client to access a mailbox in the new Wing Tip Toys Office 365 tenant using autodiscover (this depends on the autodiscover.wingtiptoys.com dns record. If there are errors, check to ensure this record has been correctly populated and is pointing to the value shown in the Office 365 portal)
    • emails from external senders are successfully received in a wingtiptoys mailbox in the Wing Tip Toys Office 365 tenant.
    • emails sent from a wingtiptoys user in the Wing Tip Toys Office 365 tenant to an external recipient is successfully received
    • emails sent between wingtiptoys users in the Wing Tip Toys Office 365 tenant is successfully received
  26. Import the Distribution groups that were exported from Tail Spin Toys Office 365 tenant
  27. The cut-over is now complete.
  28. By now, users must be able to access their emails using Outlook Web App. If they have followed the instructions, their Outlook and Mobile devices must be working as well.
  29. The mailboxes belonging to the Wing Tip Toys users in the Tail Spin Toys Office 365 tenant can be kept active for at least 30 days (this will come in handy for those cases where a user reports that some emails were not copied across). After this, the mailboxes can be backed up and then deleted (If the Wing Tip Toys user mailboxes in the Tail Spin Toys Office 365 tenant had other email aliases, on which emails were being received, it would be a good idea to configure an Out of Office rule to state that all emails sent to this user should instead be sent to firstname.lastname@wingtiptoys.com)

 

Thats it folks. After following the above steps, you would have moved an additional Office 365 domain to a new Office 365 tenant and would have also moved their mailbox data to the new tenant.

I hope the above helps those that are looking at getting this done.

Have a great day 😉

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