Hi,
Outlook Live is only available for Microsoft email accounts (such as @outlook.com, @live.com, @hotmail.com, or @msn.com). It does not currently support adding other email accounts.
If you sign in using the email address on your Microsoft account on Outlook Live. It will direct you to a temporarily assigned Outlook account for that Microsoft account or Office 365 account, which is shown in your screenshot.
If you require additional assistance, please let me know.
Stay Safe!