How licensing works for work and school accounts in the new Outlook for Windows

sgamfd DM me with your email address, so I can reach out via email and better help you debug. Faster than forums and easier to share visuals. This config works, and I just re-tested again to make sure there wasn't a regression. However, my account with both an Outlook.com and Gmail.com alias has been that way for some time. I'd guess that the change to make it the primary alias may take a moment to propagate, and in the meantime you are running into the filter that prevents the user from adding the user@gmail.com alias (without a Microsoft email address). Could you tell me at what point it failed? I presume you were able to put in the password, go through the Windows prompts and then it dropped you back into Outlook to that screen? I'd like to understand the set of steps before the error string. 

Also, do you know if this account is added to Windows already? I'm speculating now, but I wonder if the account is already added to Windows. You can see this in Windows Settings > Accounts > Email & accounts. If it's added there with its user@gmail.com address, it may still trigger that other block. I know you said you removed the Gmail alias. If you were still logged into Windows with that account, it may not have had a moment to sync and reset itself to an Outlook.com account.