Using New Outlook on Windows for personal email, calendar, and contact management
Hello, thank you for reaching out to Microsoft Q&A.
Have you saved your login credentials, particularly your username, anywhere else such as in the Password Manager in Microsoft Edge or Google Chrome?
For security reasons, only a partial email address is shown when you use a recovery email address to locate your username.
To find the full email address, please check whether it is saved in the password manager in Edge or Chrome. You can also check if you have sent any emails from this address to any of your friends’ or neighbors’ email addresses, and then ask them to share the full email address with you.
Also, check whether you have signed in to this account on Windows, the mobile version of OneDrive, or in Office apps. You can locate your username there.
For reference, see -
Check products or services where you used your Microsoft account