All attempts to send mail from Thunderbird result in the message that "log in to server smtp.mail.yahoo.com has failed" and a choice to retry or cancel. The password, and outgoing server account settings are all correct and exactly as specified by Yahoo. Any help resolving my problem sending mail thru' Thunderbird would be greatly appreciated. The problem first occurred about 7-20-17. I have done a system restore for my Windows 10 OS, but nothing I have tried has fixed the outgoing mail problem.