Thunderbird freezes for several minutes every time an operation is done while Inbox is open

I’m having the same problem on two computers. Thunderbird freezes a few seconds after launching. Restarting the computer doesn’t help; launching it in Troubleshoot mode freezes just the same – there’s nothing I can do. This has been happening for about 2–3 days.

Even though creating an exclusion for the Thunderbird profile folder should eliminate Defender from the list of potential culprits, you may still want to start Windows 11 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.

Note, Windows safe also disables WiFi. So you'd need a wired LAN connection for Windows safe mode.

Well, that's odd - I swear I had tried this at the start of my troubleshooting, but I did it just now and it worked! In safe mode, Thunderbird works normally. Thanks for the prompt!

So now what? I don't have any third-party antivirus running, just the native Win 11 defense.

Thanks for the lead!

Is there any other forgotten anti-virus/security software running on your computer? If you do have multiple profile folders, make sure the one you picked for the exclusion is the one you're having problems with.

Beyond that, https://wiki.mozilla.org/Thunderbird:Testing:Memory_Usage_Problems has a comprehensive list of troubleshooting steps.

No, no other security software running. And certainly nothing had changed the other morning when this all stopped working; this setup had been running fine for years.

Maybe that Anti-Virus is scanning every file that opened and thus taking over control albeit temporary. If you download to a file it gets opened in order to write to it. You select an email to read and file needs to get opened to read from it.

Suggest you try making your Thunderbird profile folder exempt from scanning to see it improves things. If you downloaded TB from official website: https://www.thunderbird.net/en-US/thunderbird/all/

Then it's likely this is the 'Thunderbird' folder that needs to be made exempt so AV does not scan anything it contains.

• C://Users/username.Appdata/Roaming/'Thunderbird'

Can anyone provide a step-by-step guide on how to sort this out, as I’m currently unable to use the Thunderbird client – it freezes after about 5 seconds, and the same thing happens in troubleshooting mode. For now, I’m using the BlueMail client as a stopgap, and it works like a charm. No glitches or freezes. I’m not a programmer or an IT specialist; I just want it to work! Thank You.

Can anyone provide a step-by-step guide on how to sort this out...

.Ideally you will have created your own question. But since you are here...

There is not necessarily one killer solution. Please see https://wiki.mozilla.org/index.php?title=Thunderbird:Testing:Memory_Usage_Problems

Update: I added the TB profile folders to Windows Defender exceptions again, rebooted, and now Thunderbird works nominally. I don't like having to make a security exception, but I'm glad it seems to be working. Thanks for all the suggestions and help!