You may ask why? I say why not. so it appears that thunderbird try to use Oauth2 to authenticate gmail. A few months ago this worked like charm but now it doesn’t so this seems to work best.
I will start from the beginning if you are newbie (Newbie friendly)
- If you just installed thunder bird on the top right click then select Menu bar it will add check mark.
2. Then click on Tools then go to Account settings then click on Account Actions Then click on Add Account.
3. Fill in Your Name (This can be your full name or just name) Then Email address (all lower case) then password
4. Click on Manual configuration There will be spot Authentication Method then select password on both spots. Click Done
If you get password denied error you may have to change a setting with in your gmail account to Allow Less Secured Apps they don’t have much instructions. I’m going to help you with that.
- Go to gmail.com login to it
- There will be a colorful circle on the top right side should have red,blue,green,yellow Click on it
- click on Manage Your Google Account
- Click on Security (After you click it you should see the word Security on the top right of the page.)
- Go down to the bottom of the page to Less Secure Apps then click on Turn on
5. Try to sign in to Thunderbird again. it should work.