Uh, forgot to include screenshot.

Omit the password. That is the issue.

No, that wasn't it. I still get no login screen when omitting the password. Even tried with and without a checkmark in "Remember password", but none of it makes any difference.

Puzzling. Do check that cookies are accepted at settings>privacy&security. In setting up account, just enter name and email id, nothing more. You may see a message that it's missing info, but click done anyway. That works for me, as I just tested it. But, if that isn't working, I have no further ideas on it. Gmail is a bit troublesome sometimes, for sure.

I entered only name and email address and got the same result (and no Google login page). I forced TB to save the configuration (manual, advanced, ...) but naturally it does not fetch my messages. When i right-click and select "Get messages" the status changes to "Connected to imap.gmail.com" but that is a lie (see below). However, when I pressed "New Message" and sent a message, the OAuth pop-up with Google log-in came up and I could log in and give TB access, and the message was sent - but it then (naturally) stalls when trying to save the message in the "Sent" folder. I could then send more messages - the actual sending went fine (and the messages were received in my other account) but saving in "Sent" did not.

So: TB with Gmail OAuth works for SMTP but not for IMAP.

During all this I had Wireshark inspect the network traffic. TB connects to imap.google.com on port 993 without any prior attempt to connect to a login site and when it tries to establish a TLS connection (sends a client hello), imap.google.com resets the connection. At no point will TB try to contact another server to do OAuth login and status will say "Connected to imap.gmail.com" long after the connection has been reset (closed) by the server (as that happens immediately).

Couple of things to check - it seems very odd that you do not get that initial login screen. You really need to get the incoming set up same time as smtp.

I would remove the gmail account via Account Settings and exit Thunderbird to ensure files get updated and it has been removed. Then check the following before restarting Thunderbird.

As Thunderbird is new on this computer: Check: Firewall Firewall may be the default supplied on computer OR controlled by an Anti-Virus product you installed. Thunderbird program (the thunderbird.exe file) must be set up as an allowed program. If using the default Defender I think it's here: Settings > Privacy & security > Windows Security > Firewall & network protection > Allow an app through the firewall

VPN: Are you by any chance running a VPN? If yes then you need to switch it off or create a tunnel for Thundebird to use. Gmail and many servers do not like VPN because gmail is expecting your computer IP address and if it's getting something else the server thinks someone is trying to hack your account so may just block access.

Localhost: Are you running any program that uses the 'localhost' eg: Apache ? If yes, then you need to switch if off whilst trying to set up the gmail account. You can switch it back on afterwards.

I did as you suggested and results were completely the same: Initial account setup fails (without login prompt); when I force creation (manual, advanced) I can subsequently send a mail and when I do, I get the Google OAuth dialog and sucessfully send the mail (smtp) but saving in sent folder fails (imap, no login prompt).

Notes on the suggestions:

Firewall: I already had the firewall turned off completely (but I added TB as an app anyway, just in case). I would not expect it to be a firewall problem as Wireshark shows TB successfully making the connection to the imap port (993) but failing in the TLS handshake (the server resets the connection). Also, the OAuth signin is obviously allowed for the SMTP submission, and all that is the standard https port anyway.

VPN: I am not running a VPN (and it would be unlikely to be the culprit, for the same reasons given above for the firewall).

Localhost: I don't see why this would matter at all, but anyway TB and wireshark were the only programs running.

re :On my old machine, having an older TB, I was connected to my gmail account (using OAuth authentication), so it is not a question of settings on the account.

Just a thought, but is that old machine still running - in other words are you using it to access gmail ? If yes, can you Exit Thunderbird on that machine.

It's almost as if gmail is expecting the Oauth token as if it thinks it's already set up for incoming or trying to use something else maybe a normal password or maybe expecting an app specific password.

Please confirm you are not using an app specific password. Please confirm 2 step authentication is Not switched on in the webmail account.

What have you got saved in this location: In Thunderbird.

• Settings > Privacy & Security
• Scroll to 'Passwords' section
• click on 'Saved Passwords'
• Click on 'Show Passwords'

• Suggest you remove all passwords that mention the gmail account.
• Select each line and then click on 'Remove'

Then restart Thunderbird. Does it then prompt that gmail login ?

Hi,

No, I'm not running my old machine anymore.

I don't think the problem is gmail expecting any specific credentials for my account - it never comes that far. The server (imap.gmail.com) resets the connection after receiving the initial TLS client hello package from TB - i.e. before any actual data is sent. The gmail server does not know which account is trying to connect at that point; the TLS protocol has not even been negotiated yet because the server does not complete the handshake.

About saved passwords: After initially setting up the account (forcing account creation after I get the yellow box), there are no saved passwords at all. After I send a message and successfully log onto smtp.google.com with OAuth, a "password" starting with "1//", which I assume is a token, is saved for the provider "oauth://accounts.google.com (https://mail.google.com/ https://www.googleapis.com/auth/carddav https://www.googleapis.com/auth/calendar)". This apparently does not help the IMAP connection, which still fails.