Google are not forcing anything at all about IMAP and pop at this time, Only the use of oAuth.Also removing the account is a very bad idea as a general rule. and setting a new one up is most certainly not required.

I discuss the change in my blog here https://thunderbirdtweaks.blogspot.com/2022/03/gmail-less-secure-apps.html

Thanks for prompt reply, Matt.

I have no option for changing to Oauth2 in the outgoing server settings, but do in the incoming one (I think this has changed since I started trying to change the authorisation method). I change it in the incoming server settings, and now I get 'This server does not support the selected authentication method' when trying to get messages (and no request from Google to enter my password and give permission to Thunderbird to download messages)!

Ian

I've just realised that I've not made things completely clear in my question. When I say I start the New Account config, I then ask it to establish a new account in Thunderbird, using my existing Gmail account details. Sorry for any confusion.

Ian

if your server is set to imap.gmail.com, POP.gmail.com incoming servers or smpt.gmail.com for outgoing mail then the option for oauth will be present. If you change the server name in account settings you will need to close the tab and reopen it to refresh the options available for the new server name. A bit clumsy, but that is how it works. The list is populated when the pane is displayed, not when it is edited.

SO again I will ask why you would be using the new account config? You already have the account defined. IF you actively desire to use IMAP then ok, but otherwise setup will fail because you already have an account of that name. The the existing account must be removed (usually resulting in lost mail) or renamed so it does not conflict.

The outgoing server is set to SMTP. Changing it to SMPT still does not give me an option of Oauth2 in the authentication box (even when closing the tab and re-opening it - which seems quite logical to me). The reason I started the New Account config was that that seemed to be the established wisdom on the Internet as to how to change to Oauth2. I had previously looked at the Edit-Account-Settings option (the logical route), but at that stage had no choice of Oauth2 in the authentication box...

Thanks

Ian

I am trying to alter my settings on Thunderbird (ver 68.10.0 ...)

Before anything else, update to the latest release version (currently 91.7.0). https://www.thunderbird.net/

It is recommended to create a full backup of your Thunderbird profile prior to the upgrade. https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile

I thought that I was running the latest version for Linux Lite 3.6 - this is a 32 bit machine. I got part way through the (manual) installation of Ver 91.7.0 and got a whole screen full of exemptions and errors, then it seemed I had to enter all my email account details again, at which stage I got frightened, and managed to get back to the old version. Does anyone know if Version 91 will run on Lite 3.6?

Thanks

Ian

I seem to have sorted it out - Main thing is to ensure cookies are enabled (Edit - Preferences - Privacy). Doesn't seem to matter if you set them to be cleared on leaving Thunderbird. Then proceed as in my initial post - remove passwords for relevant account, stop account checking for messages, then File - New - Existing Mail Account - enter mail account details (and password or it doesn't seem to work). A Google login screen then comes up, and all seems to work (sometimes). I had to have several goes at this stage as it would hang up - still not sure why. To alter another account it seems that you have to shut Thunderbird down and start again. It downloads all the messages for the account you have changed, even though they already exist on the local machine. Maybe there is a way to stop this, but I'm just pleased that it all works now!

Ian