Migration from one M365 tenant to another
We all appreciate how easy it is it to work with Microsoft Office 365 where so many things are automated and handled by Microsoft, but one day, if you split up your company or acquire another one, you’ll face the need to move data from one Office 365 tenant to another. This is, in fact, a very complex task, and it’s where you’ll need much deeper expertise on how things work behind the scenes.
Let's see what the choices of a migration path are:
In our experience, the data migration is just one piece of the puzzle. In most cases, you need to move the DNS , so this is a major undertaking migration and all the challenges that come with it. On Monday morning, we need to reconnect all users to the new tenant, and the process of moving it depends on the device type, OS, Office version, Active Directory, or simply the number of users devices that need to have their profiles updated day after day go-live. No tool can completely free you from this tedious task.
Typical phases of a migration:
- Study phase (Proof of concept, architecture, context exploration, tool selection, scoping)
- Prepare (setup environments, pre-stage data move)
- Communication to users
- Migration event (cutover weekend)
- Post-migration
Cross-Tenant Mailbox Migration
Microsoft is offering a preview of a new feature called “Cross-tenant Mailbox Migration.” See https://techcommunity.microsoft.com/t5/microsoft-365-blog/cross-tenant-mailbox- migration-in-now-in-public-preview/ba-p/1692465
Note that it can only migrate mailboxes; it does not cover Teams, Sharepoint, OneDrive, groups, etc. It requires Azure Key Vault and a storage account—for that, in addition to Office 365, you’ll need Azure a subscription in the target tenant. But don’t worry— it won’t use up much. Let’s outline the method used by the tool, and then we’ll explain the steps for using it.
The Microsoft method is based on a mailbox Exchange-like migration. You need to create a Mail-Enabled User (MEU) in the target environment, then run migration , and the system will copy the data and keep it in sync—once a day—until you finalize the migration (on D-Day, say two weeks later). After that, the new mailbox will be available in the target tenant. Note that on the source, the mailbox will disappear and be converted to an MEU. If email is sent to the old MEU— it —it will be forwarded to the new mailbox. This is an important difference, asthird-party tools typically maintain two mailboxes that are synchronized but both continue to exist. With the Microsoft method, only one mailbox exists at a time; the other is an MEU contact. Another prerequisite for the Microsoft method relates to AD synchronized tenants. To create a MEU, you must have a Exchange hybrid environment or, at a minimum, Exchange AD schema in the target AD domain/forest. Forthird- party solutions, a it is typically not required.
The Azure Key Vault will store the credentials (certificate), and Azure storage is simply a blob used as transfer space. Storage can be any local storage with no redundancy, for hot access only—the only thing to remember is to keep Key Vault and Storage in the same region.
Once the prerequisites are met, you can run a one-liner command for the powershell prepared by Microsoft to configure the target tenant. Then you’ll need to grant admin consent in both tenants (the URL will be provided by a script or sent via email). Finally, run another one-liner command for the source. Now you can migrate your users in batches, just as you did in the past in Exchange on-premises, or using the ` powershell New-MigrationBatch` command.
We noticed in out tests that Microsoft method is 1.12 time faster that3rd party tools. Remember - it is a preview, so do not expect a good support from Microsoft yet.
Mover.io
Your next step might be to migrate users data into OneDrive (essentially it is a Sharepoint Online). It can be done by Mover.io (acquired by Microsoft) https://mover.io/guides/migrating-office-365-to-office-365/#introduction
Mover.io provides an easy-to-understand GUI for moving data. Microsoft is preparing to release Powershell methods for moving SharePoint Online data, but the release date has not yet been confirmed.
Summary
Microsoft provides a cross-tenant mailbox migration tool, and when combined with Mover.io it , it provides the building blocks for your migration project. Both methods are free of charge and do not require Azure additional components, and it makes it a very attractive choice for quickly moving large amounts of data migration from one tenant to another. Our recommendation at this time is to hold off on using third-party tools for real-world projects until Microsoft moves from Preview to General Availability. Regardless of the tool used to move data, do not underestimate the effort required to update user profiles to connect to the new tenant after the data has been moved.
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