I have same issue, but with Yahoo and with my Cox.net emails that were transferred. Everything was working fine until late September of this year when Yahoo popups started, after updating Thunderbird to the latest windows 7 Firefox version 115 update. Attached popup screen shots for email that has problem. Thank you for help. genardini

I removed the “troublesome Yahoo email account” from Thunderbird. Then I cleaned up Thunderbird by deleting all old trash emails and compacting all the other email account folders. (Note: one of my other emails is a Yahoo account with no problems!)

The good news is Thunderbird worked fine for several days without the “troublesome Yahoo email account” and all the Yahoo popups were stopped.

So after four days or so without issues, I decided to add back the Yahoo email account in Thunderbird. It was acknowledge by Thunderbird and the configuration found in the Mozilla ISP database. I also ran a test and it passed without issue. But, when I clicked Done in Thunderbird I received an Unable To Log In At Server error and then a Yahoo popup showed up on my desktop.

At this point the problem seems to be with Yahoo and Thunderbird seems to be working properly. So my next option is to create a completely new Yahoo email name account and then give Thunderbird another chance.

If anyone else out there has any suggestions or recommendations please let me know by responding to this Mozilla Support question. Thank you, genardini

I am having the same problem. When I open Thunderbird it automatically opens my chrome browser to a link to the yahoo mail sign in screen. When I sign in, it takes me to yahoo mail. I don't know how to fix it and when I went to yahoo mail I saw on one page that it had thunderbird recognized but it said it was not in use. And the date all this messed up was 09/25/25.

It appears that you need to remove Thunderbird, run some system clean up tools, and then reinstall and reconfigure Thunderbird. Once that is done, check that Thunderbird opens and closes without opening your browser. Otherwise, something is wrong with your system configuration and Thunderbird is not the problem.

NOTE: Yahoo was recently sold to a new company which may be the source of all our email problems. I deleted the one Yahoo email account from my Thunderbird application that was a problem and now I go directly to the Yahoo website for that email. My other Yahoo emails accounts are still working fine with Thunderbird.

As far as Yahoo email problems, you need to contact Yahoo customer service, but thus far I have had no response from them or help, so best of luck to you!

See https://bugzilla.mozilla.org/show_bug.cgi?id=1997062#c20 for information about yahoo.

If you are still having trouble, please post a new question in support because I am locking this user's question.