Thanks for the screenshot. First, please double check the exact email address you use on your Pixel 8 and make sure you type the same one in Outlook on your PC. The message appears when Outlook does not recognize the account you entered. If this is a RoadRunner or Spectrum email, you need to add it in Outlook using IMAP settings from your provider because Microsoft does not host that email.
Please tell me who provides your email service, Spectrum or RoadRunner, so I can guide you to the correct settings.