I have three email accounts, one of which is yahoo, which I access via Thunderbird version 52.2.1. All has been working fine until today. I started getting a "login failed" box that says "login to server imap.mail.yahoo.com failed" with options to retry,enter new password or cancel. I have tried entering my yahoo password but that hasn't helped. Thunderbird is installed on my PC running Windows 10. I am not having this problem accessing all my email accounts on my iPhone 6. Can someone suggest what to try next? Thanks.