Dear VerlinCross
Welcome to the Microsoft Community.
I understand that you have encountered problems when configuring your Yahoo mailbox. Let me help you.
First of all, it is not clear which specific software you are referring to when you mention “Outlook 2024”, New Outlook and Classic Outlook are completely different software. Can you provide screenshots of the relevant pages, such as errors or screenshots of key pages such as the configuration screen when making settings, so that we can more intuitively understand the specific situation and more accurately help you troubleshoot.
Secondly, you mentioned that when you configure the email account in the control panel, you can see the server and download incoming emails. I want to confirm whether you have successfully configured it in the location shown in the figure below?

This actually corresponds to the configuration area of the Classic Outlook. If the configuration is successful here, theoretically, the relevant account should be able to send and receive emails normally in the classic version of Outlook. In order to further clarify the situation, please also provide a screenshot of this successful configuration page, and we can check whether there are some detailed differences based on the screenshot content.
We look forward to hearing from you. With your help and more detailed information, we can work together to find a solution. Thank you for your cooperation.
Thank you for your patience and understanding.
Forry.F - MSFT | Microsoft Community Support Specialist