1. Enable access from 'less secure' apps in your gmail account. 2. Allow cookies from google.com in TB Tools/Options/Privacy. 3. Use OAuth2 authentication with your account password.

More tips here: http://kb.mozillazine.org/Using_Gmail_with_Thunderbird_and_Mozilla_Suite

Hi sfhowes, I have the 3 items set as you describe, and have reviewed the article you linked. I have followed the settings for IMAP and SMTP as described there, but am still getting the same response. Am I supposed to be getting a Gmail login screen when using OAuth2? Because I am not seeing that, just the configuration could not be verified message. My default browser is Firefox, and I have popups unblocked there.

Yes, if you have OAuth2 authentication, you should see a browser window to login to the account. Make sure you don't have javascript disabled in your browser. Otherwise, it should work, unless you have an overzealous security or antivirus program blocking access.

Hmmm...I don't have any extensions that should block Javascript. And I would think the AV program would say something if it was blocking access. Is there a trace or something in TB that might show how far I am getting?

Javascript is enabled by default in Firefox, and to disable it you would have had to switch a preference in about:config. An AV program won't necessarily announce blocks if you have it set to scan SSL connections or to scan email. Best way to test that is to run Windows in safe mode and then try to set up the account. You might find some clues in Tools/Developer Tools/Error Console, or Tools/Activity Manager.

Verified that Javascript is enabled. Tried to run setup in safe mode, but still the same problems. I do have an account built in TB with the proper Gmail address, servers and ports, etc, as they should be - sometimes happens when I set up with manual config. But it times out when trying to retrieve mail and won't send anything.

Further note - my Gmail account is new, less than a month old. In the linked tips doc above it mentions something about an account that is less than 90 days old. Could this be a factor?

According to the article, accounts newer than 90 days may have problems connecting, but only if 'less-secure' apps haven't been allowed.

There was French user who had to change the server name from imap.gmail.com to imap.googlemail.com. Other than that, I can't see why you have problems setting up, unless you have some kind of unusual network setup, such as a VPN.

Finally got this configuration to work. My ISP also works with TB - the tech suggested setting up 2-step verification then generating an app password to use for Windows PC mail. Still took a little tinkering, but the default ports and servers seemed to work.

I'm glad it worked, but it's my understanding that if you use OAuth2 authentication, it doesn't matter if 2-step verification is set up or not. If 2-step is set up and you use normal password authentication, then you do need an app password.

That may well be. I never did understand what the problem really was, so I couldn't say one way or the other. But I do appreciate your help along the way.