There is a special setting in Google accounts to allow "less secure applications" access to your account. If you turn this off, Mozilla Thunderbird won't work to check your e-mail. This is confirmed on this page, where Google says:
Some examples of apps that do not support the latest security standards include:
- The Mail app on your iPhone or iPad with iOS 6 or below
- The Mail app on your Windows phone preceding the 8.1 release
- Some Desktop mail clients like Microsoft Outlook and Mozilla Thunderbird
My question is specially about Thunderbird... what are those security standards that it does not support?