If you merged your Yahoo and outlook mail into one to make your work easy, but now facing a problem like a yahoo mail not working with outlook. Then, there is no need to worry about it, just follow the step, and resolve your problem:
Try to remove yahoo mail and add it again
Check the configuration settings
Deeply, inspect your Antivirus, it might be the reason.
Read more: https://ityug247.com/yahoo-mail-not-working-with-outlook/