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OAuth2 not working - I get a 400 error

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Jade1
Jade1
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Gmail is making everyone change from Password Authentication to OAuth2 Authentication. It worked on one of my Window 10 laptops, but not the other. I have matched every single setting that I can find, but the new computer will not connect to Gmail - I get a 400 error.

I noticed that even though I selected SSL/TLS under "Servers and Settings", in the "Outgoing Server SMTP" menu, it lists STARTTLS for the Connection Security - using port 587, on the computer with the error. On the computer that works both places list SSL/TLS - using port 465.

Is that the problem? If so how do I fix it?

If not, what can I do? I have uninstalled and reinstalled Thunderbird on the second computer three times now.

I also spent hours with the Google Workspace AI - checking every possibility that was mentioned and nothing helped.

Please help me. Thank you!

Gmail is making everyone change from Password Authentication to OAuth2 Authentication. It worked on one of my Window 10 laptops, but not the other. I have matched every single setting that I can find, but the new computer will not connect to Gmail - I get a 400 error. I noticed that even though I selected SSL/TLS under "Servers and Settings", in the "Outgoing Server SMTP" menu, it lists STARTTLS for the Connection Security - using port 587, on the computer with the error. On the computer that works both places list SSL/TLS - using port 465. Is that the problem? If so how do I fix it? If not, what can I do? I have uninstalled and reinstalled Thunderbird on the second computer three times now. I also spent hours with the Google Workspace AI - checking every possibility that was mentioned and nothing helped. Please help me. Thank you!

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