I had been using my outlook account in Thunderbird for years, but have not for the past 2 years or so. I have multiple email accounts set up in Thunderbird now. All but one -- the outlook.com account -- work. For some reason, despite having the correct username and password, Thunderbird continues to FAIL. I've researched online and tried other server settings, and have confirmed my outlook accounts server settings on outlook.com, and have ensured the settings are identical to what is entered in Thunderbird, but nothing works in Thunderbird. Windows MAIL also works fine. Thunderbird Error is attached. As FYI, I also tried disabling 2 factor authentication in Microsoft, in case that is the issue, but that didn't work either. I also tried deleting and re-adding my outlook account in Thunderbird in case there was some new configuration on Outlook side that was not being captured in Thunderbird. That didn't work either. So now I'm at a loss! I'd appreciate ANY assistance anyone familiar with this issue can give me! In case needed, I do not subscribe to Office365. I'm only using Outlook.com, etc. Please help! Thanks in advance!