<blockquote> The one question which is relevant has 1 answer which doesn't even address the problem. </blockquote> If you want to mention it you might also post a link to it. However I doubt you have a problem in Thunderbird at all. You are just seeing the results of the problem in Thunderbird. By far the most common cause of issues in Thunderbird for getting and sending mail is anti virus programs. However you do not mention what you use, so I will just mention is generically. The second greatest issue are add-on that are not compatible with a new version of Thunderbird. In the case of Windows 10, failure to update network drivers probably places as a distant third. Then there are changes with mail providers, like they change the server settings required to connect to the server and you the customer do not make the changes when advised (sounds like I am throwing blame, but ISP's are usually pretty good at emailing changes. Their customer somewhat lest enthusiastic about implementing the changes until something stops working. Especially if they did not understand the technical issues in the email. So there are some things you can do to try and determine what is the issue, try one of the following: *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: [https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode Windows 10], [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. If that does not offer a cause; please add the troubleshooting information to your post 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. *Do you use anti-virus and firewall software? What is the version? *Who is the email provider? Please post back with this information and any other questions you might have.