Managing personal Outlook.com account settings, security, and privacy
Hello Guys.
Here is what I have done.
Go to account security .
Under More Security options >> Manage sign in option
you can create a new alias and can set that new alias as primary.
By default, our primary alias is our email address.
Once you set the new alias as primary, untick your original email then save it.
Be sure to remember your new alias because that is what you are going to use to log-in.
Don't give your new alias to anyone.. I think our email address remains the same.
This way, our original email cannot be used to login.