I wanted to remove the Hotmail account from my Outlook because the amount of spam it was getting was insane. I had also created a new one and added it to Outlook. Even though I made the new one the primary account, it wouldn't let me delete or remove it without removing the other Microsoft Exchange account. So I removed both and after that I was not longer able to access the one getting all the spam. It claimed it as a reserved domain or already in use by another account.
I just wanted to talk to Microsoft Rep which I did once years ago. Now it's like not even possible.