How to federate default domain for 365?

Question

Hello I am migrating from exchange 2013 to Exchange online and want to use Duo for federation with 365. I have a default domain of mydomain.com and i have the onmicrosoft domain. If I select the onmicrosoft domain as default I can then federate the mycompany.com domain but I can't change it back. I was wondering what are the issues if i leave onmicrosoft as the default? Can I just manually change the domain for any new user I create so they get the mycompany.com domain? Is that the ramification I will deal with in the future? Are there any other issues I need to worry about? thanks so much!

Answer 1

You cannot federate the *.onmicrosoft.com domain. You will need to federate a custom domain. So first you will need to register the domain in the Azure AD blade: https://learn.microsoft.com/en-us/azure/active-directory/fundamentals/add-custom-domain

Then you woul need to follow the steps here: https://learn.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-fed-whatis Have a look and let us know if you have questions.