Do you empty trash and Junk folders on a regular basis?

Can you use a tool to find which files in your profile are are the largest? (top 10-20)

Yes. I do empty Trash and Junk folders daily.

"Can you use a tool to find which files in your profile are are the largest? (top 10-20)"

Can you suggest a tool which will find which files are the largest?

Every time I open TB, it is unable to open a few folders. Sometimes it disables the associated filter. Or, when in the the filter dialog, there is no folder listed. After many minutes, it sometimes find the folder.

Is there a finite number of folders TB can handle?

Repairing this issue is unproductive and time wasted.

> Repairing this issue is unproductive and time wasted.

Yes, it would be.

Start with this ...

• Start Windows in safe mode with networking enabled - https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode
• Still In Windows safe mode, start Thunderbird in Troubleshoot Mode - https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird

Work in Thunderbird. Does problem change? (many users have found antivirus software causing problems)

If a new profile is created and the accounts are repopulated, is there an safe, effective to move saved data and filters?

All this began with a recent TB update in February. I recently opened TB my laptop which has not been updated. TB worked well. It's almost a carbon copy on my main units until the updates showed up.

Can I revert back to an earlier update and back out of this problem?

Safe mode in Thunderbird. Does problem change? (many users have found antivirus software causing problems)

The summary error does not appear.

Malwarebytes which has been on both platforms since purchased. As I noted yesterday, this is a new anomaly. Thunderbird and Firefox both get many more updates than my protection software.

What more can I do?

Your results suggest the problem is not with Thunderbird. You will need to adjust or remove Malwarebytes.

I stopped loading Malwarebytes and Defender, yet the situation remains.

There is anew error showing up.

Tried to create a filter 7 times, but it didn't work out. Try to move a different message. Otherwise, updating Thunderbird to a newer version might help. There seems to be an issue with message Databases not being ready when emails are moved across to a different IMAP account. We currently have a support request with the mail application teams to help us resolve this problem. Alternatively you can use 'Create Filter From Message' on the message after you moved it, or move the mail to a local folder.

What now?

Today's update: I downloaded to v115. Aside from the reconfiguration and rebuilding filters, there has been no re-occurrence of the errors previously mentioned here.

Is it the version or the new profile? This answer is beyond my skills to comment.

Regardless, thank you for all the support.

John

I found https://bugzilla.mozilla.org/show_bug.cgi?id=1919107. But so far we also don't know what is causing it.