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Tenant to Tenant Migration in Office 365

Tenant to Tenant Migration in Office 365

The number of Office 365 adoptions among organizations is rapidly increasing by the day. Often, organizations have to deal with multiple Office 365 accounts in situations like mergers and acquisitions. In other scenarios, there might be a requirement to consolidate tenants on different versions within the same organization to reduce costs and complexity of daily operations. In this article, we will explore how the Office 365 tenant to tenant migration works. We will briefly discuss the steps organizations have to take when they migrate their Office 365 mailbox to another tenant.

Snapshot of Office 365 Tenant to Tenant Migration

The Office 365 migration from tenant to tenant requires planning at least two weeks ahead of the intended date. Here’s a snapshot of the process which we will elaborate in the following sections:

  • Prepare source and target tenants
  • Create objects in target tenants
  • Prepare the domain whose user accounts are being migrated
  • Create a CSV file of user accounts
  • Set the time to live (TTL) for changing the MX records
  • Stop mail flow to the source tenant
  • Prepare the source tenant and target tenant
  • Start the tenant to tenant migration in Office 365
  • Cleanup after completion of the migration project

Pre-Migration Planning

The first step of any Office 365 migration, including tenant to tenant migration, is to plan the migration process well in advance, in most cases, at least two weeks before the scheduled date, to avoid unforeseen disruptions. Planning the process includes taking measures to ensure that the pre-requisites for the Office 365 migration are fulfilled and any other licenses for third-party migration tools have been acquired.

Preparing Tenants

The next step is to prepare the target tenant to migrate mailboxes from the source tenant. This might include creating an additional room in it to accommodate new user mailboxes. The migration process needs admin accounts for both the source and target tenants. Objects like Rooms, Resources, Groups, and Users from the source tenant will have to be created in the Target Tenant through Azure Active Directory consolidation or manually from the Microsoft 365 admin center.

Informing Stakeholders

One of the most important steps to be taken in the pre-migration stage is to inform the stakeholders about the impending process. Organizations must chart out a solid communication plan to notify users whose Office 365 tenant will be migrated. The communication should include details such as the expected time for completion, advisory to notify end-users’ contacts about the change of services and the steps they need to take after the migration process such as instructions on how to connect Outlook on the web and whom to approach for assistance.

Preparing the Domain

The source Office 365 tenant will have to be merged with the target tenant. This is done by adding the source tenant to the target tenant’s Microsoft 365 admin center and creating TXT records for DNS verification. This will allow sufficient time for DNS records propagating to the new server.

User Accounts Preparation

The IT team of the organization must generate a CSV file of the email addresses that have to be migrated to the target mailbox for using a third-party migration tool. It is advisable to append .onmicrosoft.com to the source tenants’ email addresses.

Updating Mail Exchanger (MX) Records

The MX records indicate the address of the mail server which receives emails for the office 365 tenants. When the source tenant migrates to the target tenant, the server address receiving email on behalf of users will have to be changed to the target tenant’s address. Changing the address to which the records point will take time during which period there would be a disruption in the mail flow. This period, called time to live (TTL) has to be kept to the least possible value for minimizing disruption. So, the IT team must run tests to determine the TTL before proceeding with the migration.

Disabling Azure Active Directory Syncing

The Azure Active Directory, which allows access to public folders, apps like SharePoint Online, and other resources must be forced to stop syncing before accounts can migrate from one Office 365 tenant to another. This process can take almost a day and has to be initiated early on. Any new changes in the source tenant will not be reflected once the sync is disabled. Hence, it must be planned accordingly, preferably on a non-working day.

Migration Day Activities

If you have planned your Office 365 tenant to tenant migration well, there aren’t too many activities to be performed on the day of the migration. Broadly, there are only four things to be done.

  • Stop receiving incoming emails to the source tenant.
  • Configure the source tenant domain to move to the target tenant.
  • Verify the source tenant’s domain on the target domain.
  • Select the best migration method and proceed with the Office 365 tenant to tenant migration.

Stopping Inbound Emails

The migrating server must deliver a “not reachable” message to mail servers that are trying to deliver new mails to it. It is advisable to rope in a third-party service that can queue emails for a pre-decided time during the transition period to prevent a non-delivery report from being sent to the senders.

Source Tenant Domain Preparations

The source tenant domain has to be removed from Office 365 for the migration to succeed. This entails resetting SharePoint Online public websites, email addresses, and other objects back to the initial domain. Secondary emails will have to be removed and licenses have to be revoked before migrating to the new Office 365 accounts. The processes which are blocking the removal will have to be manually stopped using PowerShell command.

Target Tenant Reception Preparation

Once the source tenant domain has been added to the target domain, the transfer has to be verified in the latter’s admin center. The Azure Directory has to be configured for the new domain in the target domain and the licenses to be assigned to users for mailbox activation. Assign the old email addresses as the primary addresses and set passwords for them. The inboxes will start receiving mails once the MX record updates are complete.

Moving Objects to the New Accounts

The Office 365 tenant to tenant migration is complete when all objects including calendar and contacts have been moved to the new accounts. There are different methods of migrations, namely staged migration, cutover migration and hybrid migration which have discussed in another blog. Use the appropriate method depending on the number of Office 365 tenants and the Exchange Server.

Post-Migration Steps

Outlook caches the list of addresses to which users send emails. After migrations, there is a possibility that the replies on migrated emails may not be delivered successfully. This issue can be resolved by clearing the Outlook Auto-Complete List.

Conclusion

That brings us to the end of the Office 365 tenant to tenant migration process. It is not every day that organizations have to migrate from one tenant to another and every migration poses a unique challenge. The most competent IT teams with the best tools at their disposal tend to seek expert assistance to find solutions to sticky problems. That is where Apps4Rent comes in. We have assisted thousands of clients to migrate to Office 365. Reach out to us for 24/7 assistance via phone, email, and chat when you need us.

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