A client came to us asking us to migrate there 2 Office 365 tenants into 1. This was going to be a task with careful planning and preparation to make sure we get this right first time.

We decided to write this blog to explain our methods and working to help any one else if they get stuck. We also offer this service as a package if this is something you need help, our team at ValiantIT will take everything from you and deliver 1 fully working tenant.

Current Setup

Tenant 1 – domain1.co.uk- 11 users – the target tenant.

Tenant 2 – domain2.co.uk – 12 users – to migrate to tenant 1

Finished Setup

Tenant 1 – domain1.co.uk & domain2.co.uk with 23 users.

First, we took to task in getting all of the emails exported out to PST files. This was easily completed with a big of PowerShell scripting. Once complete we downloaded all mailboxes to our cloud storage servers in London.

Once we had a safe backup of all email data we then proceeded to delete domain2.co.uk from tenant 2 allowing us to add domain2.co.uk to tenant 1. Once this process was complete we then started to add users/aliases into tenant1. We used an exported CSV file for this process to enable us to configure all mailboxes as like for like on the old tenant.

Successfully getting everything imported meant we can import the PST’s previously exported from Tenant 2 into tenant 1. This again was a very easy process to follow with PowerShell being so easy to use once the script was setup correctly.


The finished product was just what the client wanted, a fully working multi domain single tenant office 365 setup. We are very happy for the oppurtunity to do this work and will happily work with the client to carry out any more IT Support or projects they throw at us.