We have 1 person with a timeout issue. You. so what are the odds we have a bug and only 1 of the 2

We have 1 person with a timeout issue. You. so what are the odds we have a bug and only 1 of the 25 million or so users is affected? I would be guessing very remote.

That Nortons lies about what is enabled and fails dismally to remove it self from memory even when it is reporting same is a known fact. That you have used NIS exclusively you have no idea how much it slows machines. You would need to have identical devices with different solutions to be even able to guess at the probl;ems one causes over the other.

So I suggest;

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 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: Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, 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.