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Mergers & Acquisitions: OneDrive for Business Migrations When Merging Office 365 Tenants

Jul 25, 2019 by Mike Weaver

Merging Office 365 tenants and planning OneDrive for Business migrations

OneDrive for Business is extremely powerful. The ability to securely share documents quickly and easily allows for effective collaboration, even across tenants. However, in a Microsoft Office 365 tenant to tenant migration, this can introduce problems. 

For those of us that share and collaborate with OneDrive for Business regularly, the impact of moving can be precarious – what if you lose access to urgent documents mid-migration?  

However, as an Admin, I also know that not all users utilize these functions, or they are out of date. 

Planning OneDrive for Business access when merging Office 365 tenants

Like any IT project, clear communication is key. We spent a lot of time creating end-user communication templates for Office 365 migrations, which have been warmly received by customers. Please check them out if you’re on the migration roadmap.   

Included in some of the scripts is space for more information that is custom to your organization. OneDrive for Business sharing is a great example of this; if there isn’t a lot of use in your org, a target communication may be in order instead of a blanket communication to all users. 

To say planning is crucial for successful Mergers, Acquisitions, and Divestitures is an understatement. Scoping Office 365 tenant to tenant migrations, and their impacts, are huge.   

Thankfully, there are many great resources out there to help, and Vasil Michev has an excellent script for reporting on shared links within Office 365. It really is a work of art, and will be a godsend for anyone needing a OneDrive for Business shared items inventory 

You can find the script here: 

It will look at all files, and you can even use an option to enter your internal domains to only flag external sharing. Both options are important for your planning. 

Things to look for in the output

  • High Internal Sharing, either in volume for a user, or for high usage among your users.  
  • In most cases these items need to be reshared. This needs to be considered when evaluating end user impact and planned for. 
  • High External Sharing 
  • You may uncover a business process here that you didn’t plan for. These links will change and need to be reshared post migration. If you have a small number of users with high sharing, it may even be worth an interview to understand the use case and help them get ready for the migration.  
  • High External Sharing – To Your Own Tenants 
  • This is extremely common in Mergers, Acquisitions, and Divestitures. Using this permissions script, you can help plan and prepare users for their tenant to tenant migration. This data is also important to find likely work teams. You may want to group users sharing lots of documents with each other into the same migration batch to prevent having to reshare multiple times. This process is very important if you have multiple tenants. 


Keep in mind that resharing in staged migrations can be tricky. If a user doesn’t move with a user that they are sharing with, they may have to reshare their document twice… ouch!   


  • Mary and Bob are working together on a proposal in OneDrive. Bob is in Sales, Mary is in Engineering. Mary has the file stored in her OneDrive for Business library 
  • Mary moves from one Tenant to another Tenant with the Engineering team in the first week of the month. 
  • Mary has to reshare this document with Bob, in the old tenant, so they can continue working 
  • Bob moves with Sales the following weekend 
  • Mary has to now reshare this document back to Bob’s migrated account. 

This kind of reporting can be added to the shared analysis to help group users.  

I also have a blog that guides this from the Exchange perspective – Office 365 Migration Batches: How to Group and Wave Users 

This is a very difficult topic! Batching users is very time consuming, never perfect, and takes extensive organizational knowledge. However, for staged Office 365 tenant to tenant migrations, this is key to limiting user impact. 

Other things to consider are multi-tenant migrations. It is not uncommon for an acquired company to have multiple tenants or a company to be doing multiple projects at once. The Merger, Acquisition & Divestiture environment can be quite chaotic, but data is everything. 

One key caution hereif your organization has a very long share expiration date, many of these permissions could be out of date. Users may not even know they have access.  

This is why, in most cases, organizations do not seek a solution to automatically reshare documents in a migration. However, it also means that during planning, you need to be aware of this, so you worry about the right permissions and not stale old ones. 

One other tip: If you are a Quadrotech Office 365 Reporting customer, you can pair this data with some of your reports to help plan your tenant to tenant migration even further! 

If you’d like further information on our expert Office 365 tenant to tenant migration services, please complete our contact form and one of our migration specialists will be in touch to discuss your project.