http://www.seas.ucla.edu/gsuite/README.thunderbird.trouble -------------------------------------------------------------------------------------------------- Suddenly can not login in anymore -------------------------------------------------------------------------------------------------- Copied from: http://kb.mozillazine.org/Using_Gmail_with_Thunderbird_and_Mozilla_Suite "Gmail routinely blocks logging into a POP account so that they can show you a message. You need to login to webmail using a browser to clear it. Sometimes you can't log in because Gmail thought something suspicious happened, and set a captcha. Thunderbird has no concept of a captcha, you need to login to webmail using a browser to clear it. Similar problems can appear if you use a VPN due to Gmail detecting that your IP address is from a location far from where you normally log in. This can cause security exceptions, and force you to periodically login to google to tell them that the remote login was you. If you get a popup later on that you have to sign in to the Google account again, and then a "cookies disabled" web page you need to either enable cookies in Tools -> Options -> Privacy -> Web Content or add an exception for Google. [6] There have been several reports of a working Gmail IMAP account breaking (can't login anymore) due to the allow less secure apps setting changing to disabled. Its not clear why this occurs, but its not something that Thunderbird can change. [7] [6] REF: https://www.ghacks.net/2016/08/29/fix-thunderbird-wont-let-you-sign-in-to-gmail/ [7] REF: http://forums.mozillazine.org/viewtopic.php?p=14793120#p14793120 -------------------------------------------------------------------------------------------------- 20190313 tk#204483 tk#204497