Nothing has been changed windows updates, etc., that I am aware of? I have attached the error message I am receiving. I have already, checked my gmail account online, and all the settings are correct. I also uninstalled thunderbird, and restarted my computer, and reinstalled thunderbird, no help? So, I have a different computer that I was setting up for someone else. As a test I installed Thunderbird same version and added the user account to it that was causing me issues. It works correctly! Connects to imap/smtp no problems, but on the computer I need it to work from it does not? So I am guessing the error it is not strictly on Gmail side? Also, might not even be Thunderbird? Just not sure what is happening behind the scenes, as far as, what the process is when the computer/thunderbird sends out a request to gmail to connect to it's mail servers? Could it be some type of network card or hardware issue/glitch? Everything else appears to be working correctly on the internet.