I have no idea what "the suggested actions" are or whose suggested actions they were. Please, we know exactly what you tell us. In this case just about nothing except you have issues with yahoo. Note this URL is on your computer. No where else. That is what localhost means. What I do know is Yahoo are having issues. They are exceedingly coy about exactly what the issue is, and their suggestion of removing and replacing a password make no sense to me at all. But they are the ones with an issue they so far are not explaining so we can only follow their instructions. After watching their video I am guessing their oauth database has been lost, perhaps hacked, so they need to establish new keys, hence the re-authentication. Normally the server would refuse the old key and a new one would be generated by going through the re-authentication process. But do it their way. So you will be removing an Auth:// entry in your password manager in Thunderbird with a user name of your yahoo account. Note that password management instructions for Thunderbird are here https://support.mozilla.org/en-US/kb/password-manager-remember-delete-change-tb If you ring Yahoo do not remove any pop mail accounts, even if they tell you to do so. They like to tell you to remove the account and loose all the mail for the last however many years and just sort of hang up when you complain about the standard of support after referring the person here for some volunteer to try and glue the mess they made back together again. To quote yahoo from this page https://help.yahoo.com/kb/SLN4075.html <blockquote>We are aware some users are experiencing issues accessing their Yahoo Mail using third-party mail clients. Removing and re-entering your Yahoo Mail password or app password in the email client should solve this. Read our help article for more information and steps. You may also access Yahoo Mail on the web at mail.yahoo.com or using the Yahoo Mail app for iOS or Android.</blockquote> Their support article linked to is here https://help.yahoo.com/kb/mail/SLN36847.html '''Final Note:''' Antivirus programs (other than defender) are know to cause issues with the authentication process at the step where the results are passed back to your local machine via localhost. You may need to disable third party antivirus if that is your issue.