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.

Hi,

Thanks for your response.

The problem continued to occur in safe mode with networking enabled. As I mentioned, the only anti-virus running on this machine is Windows Defender.

BTW, I also now notice that it will sometimes freeze if I take a while writing a new message. Same freeze, right in the middle of my typing.

Is there some kind of autosave or autoclean that happens every few minutes? It's starting to look like it's driven by time, perhaps, instead of by any particular action.

What's next?

Scott

There is a known problem where TB is freezing ("Not Responding") while typing an email reply. See https://bugzilla.mozilla.org/show_bug.cgi?id=1972457#c3 for a workaround.

Thank you.

This did not fix the issue.

To be clear, this occurs whether I am typing or not. I don't even need to be in Thunderbird.

For example: 1.) I open Thunderbird. 2.) I click into another application (e.g. Chrome). I do some work. 3.) I come back to Thunderbird after about 5 minutes or more. It is in "not responding" mode

OR 1.) I open Thunderbird. 2.) I start writing an email. 3.) After about 5 minutes, it freezes, and goes into "not responding" mode.

OR 1.) I open Thunderbird. 2.) I start reading an email. 3.) After about 5 minutes, it freezes, and goes into "not responding" mode.

Is that more clear?

I think I solved this.

I noticed in my profile folder (in the Thunderbird folder in %appdata%) that one of the mail folders had a lot of content, even though that folder was empty in the application. This did not change when I ran "compact folders".

So I methodically went through and performed a "repair folder" on each local folder and each folder in my feed, and did a "compact folders" after repairing each.

After repairing and compacting one of the local folders, a group of previously deleted messages appeared in my inbox, even though they had originally been filtered directly to another folder. The same thing happened when I repaired and compacted a folder in my Feeds.

Perhaps that's a bug y'all should look at.

But after doing all of that, the original problem seems solved. And, btw, the mail folder that had phantom content is now empty.

So apparently there is some sort of cleaning or moving of messages that occurs on a regular schedule, which was causing the app to freeze?

Thanks for helping me rule things out. Hope this helps someone else.

Scott