I have just updated TB to 128.9.1esr, and the problem remains.

128.9.1esr release notes page shows"There's Nothing Here"

Change the frequency of mail checking to 10 minutes. Does the "problem" still exist?

The original interval was 5 minutes. I shortened it to 1 minute and did not see any difference, as I mentioned earlier. I have just changed it to 10 minutes and seen the hanging after the change.

128.9.1esr release notes page shows"There's Nothing Here"

There was a brief period yesterday when they were not available. You should see them now.

See https://wiki.mozilla.org/Thunderbird:Testing:Memory_Usage_Problems

Hallelujah!!! I have finally solved the problem. I found that the Junk folder caused TB to hang this morning. I tried all kinds of things with this folder and rebuilding the folder eventually did the job. Once the Junk folder issue has been addressed, TB no longer hangs. Everything is back to normal.

@Hong, thanks for posting your solution.

Did your junk folder have 6000 messages when you did the rebuild, as mentioned at https://support.mozilla.org/en-US/questions/1506134 ?

@Wayne, let me clarify this. 1. Before I ran into the latest trouble - TB hung while I was manually downloading new messages, the Inbox had about 1k messages. 2. After I had the trouble and restarted TB, the Inbox had zero messages. I was scared. 3. After I downloaded new messages manually, which was what I had been doing for a while since the start of the hanging problem, the Inbox had over 6000 messages, most of which were junk. 4. After I manually ran the filters, the Inbox was back to normal - junk and other messages were moved to their appropriate folders. 5. The junk folder had about 3k messages during this saga.

I was able to resolve this issue last week, but my problems seemed to come from the Trash folder. System would hang consistently anywhere from 3 to 5 minutes of use while reading or composing emails. It would also immediatly hang when ever I clicked on the trash folder. Since I could not access trash anyway, I right clicked the trash folder and was able to click on Empty Trash. After I did that Thunderbird has worked as it should and has not gone unresponsive since.

I tried to empty the Junk folder, and it always hung. It looks like a recent version corrupts some folders.

I tried to empty the Junk folder, and it always hung. It looks like a recent version corrupts some folders.

But, did you click on the Junk folder first?

Because right+click on the junk fold and do empty, it should not try to access the messages, and therefore even if the folder is corrupted it shouldn't hang. It zeros out the folder. Trash folder works the same.

I first left-clicked the Junk folder, and it always hung, as I reported in my other question. After that repeated hanging, I restarted TB and right-clicked the Junk Folder without left-clicking it first to select Empty Junk, and TB also hung. I also repeated this a few times. If I had left-clicked the Junk folder, TB would have hung, preventing me from seeing the Empty Junk menu item. I was able to see the Empty Junk item because TB did not hang until I selected Empty Junk.

If there are still problems after "Empty Junk", 1. stop Thunderbird 2. find the Junk and Junk.msf files for that mail account in your Thunderbird profile https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data 3. move them to a safe place outside the profile. 4. Start thunderbird

Does the problem go away?

I cannot tell whether this method would have solved my problem because the problem no longer exists after I rebuilt the junk folder, as I stated a week ago.