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How to plot out an Office 365 tenant-to-tenant migration

IT pros in organizations on Office 365 that undergo a merger or acquisition will have their work cut out for them to successfully execute a data migration plan between tenants.

With the number of users and organizations on Office 365, circumstances will inevitably require some of them to move between tenants.

An Office 365 tenant-to-tenant migration can occur for several reasons, such as after a merger or acquisition or part of a company gets sold. These business events come with complicated legal maneuvers with rigid timelines. Most of these situations require completing tenant-to-tenant migrations on a schedule made by lawyers and executives with little to no regard for the time it takes to move the associated data. It's up to the technical team to work out how to complete the migration and meet their deadline.

Whatever the reason, successfully executing a tenant-to-tenant migration within Office 365 is a complex process with some significant limitations. Let's walk through the process to clarify what's involved with this type of data migration process.

What data can migrate?

The biggest challenge with an Office 365 tenant-to-tenant migration is knowing what data you can and cannot move. Microsoft develops new APIs continuously to give access to different types of data stored within Office 365, but as of publication, the accessibility is still somewhat limited.

To further complicate the issue, there is no Microsoft tool to move data between tenants. While there are many third-party applications to help migrate different types of Office 365 data between tenants, they all have different capabilities. Finding the right product for your Office 365 tenant-to-tenant migration requires some research to find the tool -- or tools -- that move the data your organization needs.

While there are many third-party applications to help migrate different types of Office 365 data between tenants, they all have different capabilities

Out of the entire Office 365 suite, Exchange Online, SharePoint Online and OneDrive for Business are the applications most commonly affected by this tenant migration effort. While there are multiple tools available to move these data types, this article can't pick the right one for you.

The more popular and capable migration tools are BitTitan, Quest, ShareGate and AvePoint, which acquire new features and updated functionality regularly. My recommendation is to look at these tools and other similar ones to decide which one is best for your circumstances.

Different applications come with different complications

Not every application handles data the same, which further muddles the tenant migration process.

a move between Office 365 tenants

For example, Skype for Business is an important communication tool for many organizations, but much of the data it uses is not with the application. The meetings data resides in Exchange and buddy lists live with the Skype for Business client. Most of the time, Skype for Business is not migrated between tenants but reconfigured at the destination tenant.

Teams is another application that presents a migration challenge. As of publication, Microsoft has not finished the APIs that will let third-party tools handle these tenant migrations. At the moment, you can move the SharePoint document libraries attached to Teams or the Exchange mailboxes that hold Teams calendars, but it's not yet possible to migrate Teams entirely.

Preparing for your migration

As you inventory all the Office 365 applications that hold user data that you want to migrate, the list might overwhelm you. If you need to move mailboxes and data from multiple web applications such as Yammer, Bookings, Planner, Delve, Flow, Forms, Power BI, StaffHub, Stream, Sway and To-Do, then that's going to take some work to get a handle on what is involved with each service.  

To further complicate this effort, you'll find most of the Office 365 applications don't support any migration. If you need data from a particular application, all you can do about it is try to recreate the data in your destination tenant the same way you did in the original tenant. Identifying what data you can, and cannot, move between Office 365 tenants is an important step, but it's just the beginning of your migration process.

Another issue that can complicate the tenant migration timeline is bandwidth throttling. Microsoft controls the rate of speed when transferring data on Office 365 to ensure the health of the overall platform. This limitation can be very troublesome when you need to move a large amount of data in a short amount of time.

You can try to adjust the throttling on your Office 365 tenant if you open a support case with Microsoft, but there are no clear rules on how much, if at all, the throttling limits can be relaxed. In my experience, Microsoft will do everything possible to help you reach your deadline if you explain your situation.

Tenant names and vanity domains can be another difficult part of an Office 365 tenant-to-tenant migration. All Office 365 tenant names need to be unique. This can make it difficult to find a tenant name that matches the name of your organization. Furthermore, a vanity domain -- -- can only be associated with a single Office 365 tenant. Exchange migration tools need to connect to the source mailbox and the destination mailbox by name, so most tools recommend making that connection using the address for each mailbox.

The best advice I can give is to make sure you understand the tools you chose to move data between Office 365 tenants. They all have recommended configurations that will make this work go much smoother and bring you much better results.

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