What are the settings? Do they match the ones here? https://autoconfig.thunderbird.net/v1.1/gmail.com I see you are using Linux, something I like to avoid because nothing is the same from distribution to distribution, or even download source. So you will need to offer up that information. Go to this link in Google and ensure that the chosen protocol is actually enabled from their end. https://mail.google.com/mail/u/0/#settings/fwdandpop Gmail requires oath authentication and on Linux people have this habit of disabling cookies which are required for oath. This article written when the automatic conversions to oauth were done contains good information and troubleshooting steps. https://support.mozilla.org/en-US/kb/automatic-conversion-google-mail-accounts-oauth20