What's your OS?

opening my pc in safe mode, doing this and opening Thunderbird in safe mode.

And what happened then?

Hi OS is Microsoft Windows Thunderbird opened but curser just spinning and then Thunderbird not responding message again. No emails downloading.

What is your anti-virus software?

Try to start Windows 10 in safe mode with networking enabled.

Does the problem go away?

Windows safe mode disables anti-virus software. This is a troubleshooting step, not a solution.

Thanks, I'll try that

I have a new protection recently installed by Microsoft, Microsoft Defender. My main protection is Malwarebytes.

I have removed Microsoft Defender and then tried starting my PC in safe mode, Thunderbird still not responding.

I have a new protection recently installed by Microsoft, Microsoft Defender.

Windows 10 and 11 have Microsoft Defender built-in. What do you mean with "I have a new protection recently installed ..., Microsoft Defender". Which version of Windows are you running?

My main protection is Malwarebytes.

I'd rather stick with Defender, and get rid of Malwarebytes.

I have removed Microsoft Defender and then tried starting my PC in safe mode, Thunderbird still not responding.

Can you confirm you did start Windows in safe mode with networking enabled?

The safe mode instructions are https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode

Also, in Windows safe mode, start Thunderbird in Troubleshoot Mode - https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird

Does problem change?

Hi Thank you for this, I hadn't been doing the correct safe mode start up. I followed your instructions and Thunderbird loaded Ok and I could access 2 of my accounts the 3rd was 'not responding' but then opened Ok. I closed it down then opened up again and all was Ok. It is now working as normal not in safe mode.

What is it that causes this problem?

What is it that causes this problem?

Most likely your anti-virus software. To avoid problems in the future create an exception in your anti-virus software (or an exclusion in case of Windows Defender) for the Thunderbird profile folder, so that the anti-virus real-time scanner will not scan it. https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_how-to-find-your-profile

I closed it down then opened up again and all was Ok. It is now working as normal not in safe mode.

Without creating an exception it's quite likely that the problem will return.

The (Not Responding) issue has been happening for a while now. Not sure when it started, but I'm pretty sure it mostly happens when I'm downloading email, and typically when I get to my desk in the morning, which surprises me, because I leave TB running 24/7 pretty much, and the emails didn't all just start downloading when I sat down.

I have six IMAP accounts set up, and yes, some have as much as 4.5 GB, but the accounts that generally get deluged with the most emails overnight are the accounts that are kept to under 50 emails in the inbox, total.

One would think that TB would be multi-threaded so one could write an email without having to wait for up to five minutes while TB is dealing with whatever it's dealing with. I heard this was going to happen back in 2021, but I don't see where to turn that on in settings.

Running 115.10.1 (32-bit) on Windows 10 Pro version 22H2

BTW, if you do a search for "Not Responding" on this forum website you will find nearly 2,000 threads. Not a good sign.

Mik Muller,

please start a new topic for your problem. https://support.mozilla.org/questions/new

a.allison269, did the exception help you?

@mik, also do https://support.mozilla.org/en-US/questions/1446103#answer-1651911 before filing your own topic.