April 2018 – The Mystery of the Reserved Domain

Some of you may have already known about this, but it is unlikely you would come across this unless you have curious users.

When you have a new or existing O365 Tenant and you want to add a custom domain, and you receive the following message:

Your domain cannot be added or verified at this time because other people in your organization have signed up with domain.com email addresses and the domain has been added to another Office 365 tenant. To continue adding your domain to this tenant you will need to remove it first and add it back again.

Wat?

What you may not know, is that Office 365 Shadow Tenants exist out in the wild.
These can be created when you sign up for a PowerBI trial with a Work email address.

You will need to do a Admin takeover on the Shadow Tenant, there will be a link with more information that leads you to a PowerBI log in portal or you could sign up for trial with another email address with the same domain.
Once logged in you will enter the required details in DNS TXT records to prove you own it and the takeover process is completed.
Remove the domain from the tenant and then go about adding the domain to your production O365 Tenant and off you go on your merry way. 🙂

Of course this does leave you with another tenant with a similar default domain name as your actual one. Or a third one if you let the CSP run up a new one instead of associating the actual one to Partner with. 😦