Hi, I have used Thunderbird as a client for my Gmail email account. On 5 different Computers, over 6 years, running XP - 7 - 8.1 - and now 10. Suddenly yesterday Gmail rejects the Thunderbird password. I get this error message "Sending of password for user jstevens1fkp@gmail.com did not succeed. Mail server pop.googlemail.com responded: Web login required: https://support.google.com/mail/answer/78754" I have found dozens of others getting that same message and problem. NOTHING has changed in Settings or Updates for either Thunderbird, Windows 10 - or Gmail. I have triple checked all settings, permissions, passwords, etc. . I have spent 1 1/2 days, tried every suggestion I found, nothing helps. I have another Windows 10 Computer here, There is no problem using Thunderbird for Gmail. Tried System Restore to when it was working, no help. There is no problem using my password to access Gmail via a Browser. The only thing I have not tried is deleting Passwords on both Tbird and Google, creating a new Password. HELP!!!