When setting up Office 365 a default domain account.onmicrosoft.com is setup. This domain cannot be removed. An administrator account is  created as part of this domain. It has the email address [email protected]. The administrator needs to use this email address to log on to Office 365. What if you want to use your own email address instead? It took me a while to figure out how to change the the default email address to my own email address.

You change the email address from [email protected] to [email protected] by following the steps below:

1. Log onto the Office 365 admin center.
2. Click on Admin on the top right hand side.
3. Select Office 365 from the drop down menu.
   

   Log onto Office 365 admin center

4. Click on Reset user password from the admin shortcuts on the right hand side of the screen.
5. Select the administrator that you want to change the email address of and hit enter or click Edit.
6. Change the domain suffix.
   

   Change the default email address

7. Click Save.

After you changed the email address suffix the [email protected] is the primary email address and needs to be used to log in. You will be instructed to log off and on again. After saving it can take up to 15 minutes for the change to propagate to all systems. Give it 15 minutes and everything should be working normally again.