Pro tips for a smooth Office 365 cross-tenant migration process

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Cross-tenant migration is a phrase that every IT admin is acutely familiar with. Whether you’re onboarding your organization to the Microsoft cloud or moving and consolidating your organization between tenants, you’ll need to learn best practices for Office 365 tenant migrations.

Migration is an area of your job that is not only important but may also be a source of… erm, shall we say, challenging surprises. While most professionals don’t like surprises (especially challenging ones), you can safely argue that this is even more true in the case of IT professionals, where the stakes are so high for your organization. That’s why developing a strategy for a smooth Microsoft 365 migration is so important.

What is a cross-tenant migration?

Cross-tenant migration typically occurs when your business is going through a merger or acquisition. It usually makes sense to combine numerous Microsoft 365 tenancies into one tenant in order to enhance management, boost security, and maximize collaboration across many teams.

There are a few common scenarios where cross-tenant data migration makes sense:

  • If your company has been taken over or divided
  • If your organization is composed of scattered businesses (where a migration will help to establish a centralized IT integration)
  • If, unchecked by the IT team, a portion of your organization introduced new tenants

The goal of a tenant-to-tenant migration is to move content, such as SharePoint sites, Teams channels, shared drives, and Planner plans, from one tenant to another.

Plan for identity and access management (IAM) from the start

Handling the identity components of a Microsoft 365 tenant-to-tenant migration is arguably one of the trickiest aspects to manage effectively. Every project is different, and there are several courses of action to choose from.

Some of the things people place in the identity category include user and service accounts, Azure AD guest users, application registrations, domains, third-party identity management solutions, contacts, and distribution lists.

So what does IAM look like?

In a nutshell: You need to centralize IAM by establishing directory synchronization between the source and destination tenant and declaring the source Azure AD as authoritative (for moving items).

Let’s say, for example, that your organization has 25,000 end users and you acquire a business with 500 end users; the new business must abide by the new parent company’s rules. In these situations, the majority of enterprises will provision and migrate new accounts to the destination.

Bringing the end users under their own security management is one way to overcome problems when the acquiring firm does not wish to bring the source environment up to par with their standards. Frankly, this is a faster and simpler solution.

Planning for AIM might help to assess whether or not you are ready for migration. Still unsure if you’re ready? Ask yourself the following questions:

  • How will directory objects for both the source and the target tenants be acquired and kept up-to-date throughout the migration project?
  • Does a trustworthy directory exist?
  • Will account disablement, attribute modifications, and removals be kept across directories?
  • Has the target tenant generated the relevant accounts and groups that are currently present in the source tenant?
  • Are there certain matching property values that can be used to link objects together?

You might discover that your business isn’t quite ready to start migrations based on the responses to these questions. It’s crucial to think through how to control identities access throughout the migration process.


Tenant-to-tenant migrations

How to efficiently plan and execute migrations for mergers & acquisitions or a reorganization.

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What to think about when preparing your source tenant

The first step, like with any migration, is to make the necessary preparations in your source tenant. There are two high-level steps to keep in mind during the preparation stage:

  1. Analyze and define
  2. Plan

1. Analyze and define

You will need to identify applicable quantity structures, pre-existing configuration parameters, and the data volumes to be transferred—but in order to do so, IT professionals must first conduct an analysis of the source environment.

Some big questions may be answered at this stage. For example, are we making the necessary modifications in the target environment? This can only be identified by investigating the initial situation in the source tenants. ShareGate can help with this.

There are loads of features in the “Plan” section of the ShareGate app that will give you all the visibility you need. For example, our source analysis report will give you insight on exactly what you have and where it’s located. That’s just the tip of the iceberg; we offer an abundance of targeted reports to ensure you aren’t jumping into your tenant-to-tenant Microsoft 365 migration blindly.

Then, you formulate a vision of the architecture from the current state to the target state for the migration. If you want to identify the target state and the procedures to get there (which you definitely should), then you have to prioritize understanding your source environment.

2. Plan

The next step isn’t a surprise! Once you have a thorough understanding of your source environment and have defined your target environment, the planning begins. IT experts will define each migration phase as well as design the necessary structures.

At this point, the migration timeline is important.

A good plan also defines how to communicate to end users about the transfer as well as how to proceed without imposing too many restrictions on the end users’ work.

Related: Build a great SharePoint migration plan (the contents in this article are applicable for office 365 migrations too)

Are you migrating mailboxes? What you need to know

If you’re migrating mailboxes from one tenant to another, there are some important questions to consider.

Firstly, you should be thinking about whether you’ll use Microsoft’s native migration tool or a third-party cloud migration solution. ShareGate doesn’t offer mailbox migration as part of our offerings, but there are other excellent solutions out there that can meet this particular need.

Although Microsoft’s native migration functionalities are incredibly helpful to Microsoft administrators, you should be aware of a few limitations before opting to use this solution to move Exchange Online mailboxes for an enterprise migration.

Microsoft recommends using a third-party Microsoft solution provider for your mailbox migration if you need to transfer more than 500 users or a sizable volume of SharePoint data.

High-level planning for exchange online

Once you’ve established how you’ll be executing the migration based on your needs, the next logical step is planning. Before we get into the nitty gritty, there are a few big-picture tasks to remember:

Migration application licenses: Don’t forget to purchase the required licenses for your migration if you’re utilizing a third-party solution to move your users. You need to have enough licenses to ensure that the target Microsoft 365 organization can accommodate all the mailboxes that will be migrated from the source tenant.

Communication for migration users: You must also create a communication plan. It’s essential to inform all end users about the migration as well as any service changes before it happens, and keep them in the loop during and after to keep business operations flowing as usual.

What to do three days before “the big day” (migration day)

First, you need to prepare the domain for migration by beginning the domain verification process for the target tenant. Next, you’ll need to schedule the migration. Then, you’ll schedule the TTL test and disable directory sync in the source tenant.

Migration day is here! What now?

First you need to change the principal MX record for your domain from Microsoft 365 to a domain that is not reachable, such as When Internet mail servers try to deliver new mail, they will queue it and make a second delivery attempt every 24 hours.

Prep the source tenant: Before the domain can be transferred to the target tenant, the original email domain must be deleted from all items in the source tenant.

Prep the target tenant: First, ensure that the old domain has been verified in the target tenant. After removing the domain from the previous tenant, you might need to wait an hour.

And now, the migration begins!

If you’re migrating for more than 500 end users or the native migration tool doesn’t meet your organization’s needs, now’s the time to migrate with your third-party tool of choice.

Using Microsoft’s native tool for mailbox cross-tenant migration

For some IT admins, it’s obvious whether or not Microsoft’s native migration tool will meet the needs of their organization. But for others, it’s not totally clear.

Microsoft’s native migration functionalities are immensely beneficial to many Microsoft administrators, and it’s worth considering whether it will work for you. Either way, you should make sure to have all the facts and be aware of a few limitations before choosing to use this method to migrate Exchange Online mailboxes for an enterprise migration.

If you’re trying to decide whether to use the native tool or a third-party tool, you should ask yourself these questions:

Is time a factor? The native solution has a complicated implementation process so it will take longer.

Do you need to filter what is migrated? The native solution doesn’t offer this functionality.

Do you have the resources and expertise within your team to write and manage the scripts for this project? Third-party tools offer no-code solutions.

Do you hope to transfer the mailboxes based on delegates in order to keep those permissions? In order for permissions to migrate completely when using the native solution, mailboxes containing delegates must be moved in the same batch, but unfortunately, many permissions fail to migrate at all.

If you answered no to all of these questions, the native tool may suit your needs. If you answered yes to even one of these questions, you should consider using a third-party tool for your mailbox migration.

Data analysis during and after migration

In the world of IT, there’s no such thing as too much visibility into your environment. That’s especially true during and after cross-tenant migrations.

During migration

Data analysis is a critical part of planning before a migration to avoid disappointment—ShareGate’s source analysis report fulfills that need and beyond.

  • The source analysis will show helpful details including:
  • The size of the environment
  • The total number of Site Collections
  • How many of its total Sites have been inactive over the past six months
  • The overall quantity of workflows
  • A collection of many things that need your attention beneath the Warnings and Errors section of the report.

The source analysis report is just the beginning. We offer many other super useful reports that will help with your migration, including (but not limited to):

After migration

While there’s no denying that data analysis is a crucial step prior to migration, don’t overlook the importance of reporting after the migration is complete. At this point, it’s time to test everything out to validate that it’s all working as it should.

You can count on ShareGate’s Microsoft 365 migration tool to give you the facts. It logs every success, warning, and error that happens during your migration, then organizes it into a digestible report so you can ensure that everything migrated successfully and see which areas need some help.

Once you’re confident that the high-level stuff is taken care of, it’s time to get into the details. With the help of detailed technical reports, you’ll be able to fill in the blanks, modify information in bulk, fix links, and ensure that your new environment is precisely how you want it.

Our reporting tools offer support as you:

  • Test all workflows
  • Check user permissions
  • Create a backup of your new environment
  • Switch source to read-only mode
  • Remove access to the old SharePoint
  • Run a full crawl
  • Run a script to remove sharing links
  • Get the migration approved by key users
  • Check in with end users to see how they are adjusting to their new environment

We know that your job doesn’t finish when the transfer is complete—in reality, your job is never done!

Your environment will always be growing and changing as end users continue to create new content. In order to best reflect how your ever-changing organization is structured, you’ll continue to be presented with new reasons to move teams or channels. You’re always ready to uncover vulnerabilities or errors and nip them in the bud—ShareGate provides you with the tools to manage your goals with ease.

Plan for a successful migration

The objective of a tenant-to-tenant migration is to move content from one Microsoft 365 tenant to another destination environment. With such a major transition, there are some critical questions to consider. For one, what are you migrating? Is it user accounts, email inboxes, OneDrive files, SharePoint data, team content, or all of the above? Are your source and destination tenants adequately prepared? Do you have a plan in place for identity and access management?

Lastly, do you have optimal visibility into the environments with all the relevant information? The analysis is crucial before, during, and after a migration, providing invaluable insight that will lead you on a path to success. Data gives you visibility, which means you have everything you need to make effective and relevant decisions. ShareGate’s wide range of reports paired with the user-friendly migration tool are a dynamic duo when it comes to ensuring smooth Microsoft 365 cross-tenant migrations.

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