Using Classic Outlook on Windows for personal email, calendar, and contact management
Hi. I'm Brian and I'll try to help.
This forum is dedicated to problems using Outlook online by accessing https://outlook.live.com/ using a web browser. The image you included indicates that you're using classic Outlook, not Outlook online. Classic Outlook is covered in a different forum.
The message you included means that the Outlook client cannot connect to the incoming server. You say you can log into your Yahoo mailbox using your sbcglobal.net address and see messages. Have you tried to update the password in the account settings? Do you have two-factor authentication enabled for the account or passkeys? Did anything change on your computer between when it last worked and now, like an update to Microsoft 365/Office? What version of Outlook are you using?