To diagnose problems with Thunderbird, 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 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.

Hi Matt, thank you so much for your help. I downloaded SeaMonkey last night and that was also timing out. That told me it wasn't Thunderbird that the issue was with but I've done all of the above as well as uninstalling everything I've installed since I got my new SSD installed a couple of weeks ago. I wasn't able to use networking in safe mode despite selecting it on the restart. I'm now doing a reset because it's the only place I can think of to go now. Next step will be to speak to the people who installed the SSD. I keep my computer really lean btw, I only install about five programs that I've used for years, along with Thunderbird, AVG free and Zonealarm free firewall - I disabled both but TB still didn't connect. I'll get there, hopefully! Thanks again :)

I would suggest you try simply uninstalling AVG and see if that causes issue or fixes them. I am using only windows defender on windows 10 for the past few months and I am noticing no reported infections. Now I need to decide if the experiment is over and renew my AV license. I am not leaning that way at the moment.

I finally got to the bottom of it, or I think I did, anyway. I reinstalled thunderbird and tried to set up my email accounts but it just wasn't working. I walked away from the computer for a bit and when I got back, it was working fine. I am 99% sure it was a microsoft server problem as it started to happen on my other computer too. One frustrating thing though, I tried migrating my email accounts and all thunderbird settings by copying the profiles folder to the profiles folder on the rebuilt laptop but it just wouldn't work. I've done it a dozen times or more prior to yesterday but it refused to work. I've finally done it though, it took me three hours though, I've a lot of email accounts! Thanks again for your suggestions!

ETA: one hour on and it's timing out again. I'm going to need to do some research regarding the servers, maybe others' are in the same boat.

I am so frustrated. I was having this problem with my CenturyLink email. Lots of others with the same provider were having the same problem. So I dumped that address and opened a new gmail account. It was installed into Thunderbird with no problems and worked just fine for a week. Now, suddenly, I'm getting this same "timed out" error and cannot access any of my email by way of Thunderbird. Strangely enough, I can SEND email. I can't buy the suggestion that it is a problem with anti-virus software because it worked perfectly for a week. What is the answer?

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   CarolynHoglin said

I can't buy the suggestion that it is a problem with anti-virus software because it worked perfectly for a week. What is the answer?

And it updates what every three hours. But unless you are interested in trying to find an answer instead of discounting know problem making products basis you don't think it is it, I am out of here.

The standard diagnostic process is described below, good luck.

• Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). On the Help menu, click on "Troubleshoot mode". 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.

I'm still getting this problem intermittently. It's fine for a while and then for no apparent reason, I can't access my emails for a few days unless I log in via the web. It's frustrating to say the least.

It's exactly the same with Sea Monkey. I don't know if TB and SM are in any way related but if not, it has to be something on my computer although I've uninstalled everything and it still happens. Sometimes if I reboot my computer half a dozen times TB will work again for a while before timing out. I've always got to the bottom of these things but this one has stumped me.