If you forgot your Microsoft account email address or you signed in and got the error message, That Microsoft account does not exist, we recommend following the steps in this order to assist you with finding your username.
Tip: This option won't work if you don't have security info set up on your account or if you can no longer access that security info. Move on to the next step: Step 2: Check products or services where you used your Microsoft account
Lookup your username if you have security info set up on your account
If you previously set up security info on your Microsoft account, you can use this option to retrieve your username.
Look up your username using your security contact phone number or email address.
Request a security code to be sent to the phone number or email you used.
Enter the code and select Next.
When you see the account you're looking for, select Sign in.
You weren't able to find your username...
If the username lookup wasn't successful, for example you hadn't set up or no longer have access to your security contact information, try looking for your Microsoft account username within other products or services that you know are associated with that account. See