GMAIL is rejecting TBird on security grounds!
My version is 52.2.1 (32-bit). Gmail rejects password saying Thunderbird is not secure.
My version is 52.2.1 (32-bit). Gmail rejects password saying Thunderbird is not secure.
Opaite Mbohovái (1)
You can either configure Thunderbird to use OAuth2 as authentication method or configure GMail to allow access "for less secure apps" as they call it.
To change the authentication method in Thunderbird open the menu Tools > Account Settings > [gmail account] > Server Settings and choose OAuth2 as authentication method. You should do the same for your outgoing server (SMTP) settings.
To change things in GMail, google for "less secure apps"…