Duplicate of posting to the other thread. ''Matt [[#answer-867477|said]]'' <blockquote> @Rpbert Goodman. So far I have seen two insulting topics. lambasting us as amateurs that is hardly the way to get friendly responses from volunteers. We do not deny we get no pay to help here. But then the whole Thunderbird project is a community open source project. We have no employees and no funds and in the furure may not even be affiliated with Mozilla. If you want a better service I suggest you donate to keeping the project alive into the future. https://donate.mozilla.org/en-US/thunderbird/about/ @Dubber29, Th error you posted talks about a proxy. The most common of those are anti virus programs. So I am assuming your anti virus is borked and does not know it. I suggest a reboot and if that does nothing here are some things to try which might narrow down to scope of the cause; *Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). On the Help menu, click on "Restart with Add-ons Disabled". If Thunderbird works like normal, there is an Add-on or Theme interfering with normal operations. You will need to re-enable add-ons one at a time until you locate the offender. *Restart the operating system in '''[http://en.wikipedia.org/wiki/Safe_mode safe mode with Networking]'''. This loads only the very basics needed to start your computer while enabling an Internet connection. Click on your operating system for instructions on how to start in safe mode: [http://windows.microsoft.com/en-us/windows-8/windows-startup-settings-safe-mode Windows 8], [http://windows.microsoft.com/en-us/windows/start-computer-safe-mode#start-computer-safe-mode=windows-7 Windows 7], [http://windows.microsoft.com/en-us/windows/start-computer-safe-mode#start-computer-safe-mode=windows-vista Windows Vista], [http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/boot_failsafe.mspx?mfr=true" Windows XP], [http://support.apple.com/kb/ht1564 OSX] ; If safe mode for the operating system fixes the issue, there's other software in your computer that's causing problems. Possibilities include but not limited to: AV scanning, virus/malware, background downloads such as program updates. I just noticed the split personality of this topic. So will duplicate this posting here https://support.mozilla.org/en-US/questions/1118898 I suggest dubber20 that discussion continue there and that you both post troubleshooting information to your respective threads. '''To find the Troubleshooting information:''' * Open Help (or click on three-line-icon and select Help) * Choose Troubleshooting Information * Use the button Copy to clipboard to select all. Do not check box "Include account names"! * Paste this in your post. </blockquote>

Belated, but this is the answer, it just took a long time to happen to me. http://thunderbirdtweaks.blogspot.com.au/2016/06/hotmail-proxy-errors.html