I'm not familiar with how Gmail Workspace works, and I'm surprised you may even use Thunderbird automatic configuration with a custom domain email address, but one thing that could be going on here is that, even though Thunderbird appears to be able to automatically configure your account, maybe Thunderbird doesn't do that correctly because it doesn't realise it is a Gmail account and hence doesn't automatically configure it as described here:

https://support.mozilla.org/kb/automatic-conversion-google-mail-accounts-oauth20

So something you may try is choose Configure manually and make sure you do it according to that article, in particular choose OAuth2 for authentication.

Hello and thanks for taking time to answer me. Yep, I tought about changing to OAuth2 but I don't see it in connexion securities for outcoming server However, I see it in incoming server. I've changed it but it's not working anyway.

I guess it's because the article says that it's not done automaticaly on thunderbird version older than 91.8. The one I use is the latest one.

Also, on my old laptot I did it automaticly and it worked fine.

Hmmm… Don't ask me why that seems to only be the case for the outgoing and not the incoming server, but Thunderbird seems to only offer the OAuth2 authentication option there when it knows/detects the server supports that.

Do you still have access to the old computer to compare the server settings in both? Could it be that the mail server names are wrong? Not that I know what the right ones should be, mind you, I don't know how to figure that out in your case. How Gmail Workspace accounts with a custom domain are supposed to be set up in the mail client is still a mystery to me. If Google has documented that somewhere, they've made a good job hiding it… How do you know those are the mail servers you should use in Thunderbird?

I know because I checked the setting in my old computer. Everything is the same. It's a total mystery but I'm quite sure it has something to do with OAuth2 and the fact that I'm using a workspace google acount controled by my employee (I asked thye didn't block thunderbird on their space).