Thunderbird goes very busy too often and that is making it hard to be productive in any way.
Thunderbird has been frequently "not responding" in windows more and more frequently and for longer and longer period of times. I have 4 different email accounts with thousands of emails each. I also get frequent crashes. I'm on version 90.10.0 (32-bit). I'm going to have to find a new mail client if this keeps up. There is nothing I can find to do file maintenance other than Compact and it often says something else is blocking it.
Wšě wotmołwy (1)
It may be that you have a Trojan virus infection which is downloading multiple files and replacing attachments in your emails with infected files. I have had this problem in my IMAP inbox folder in my Thunderbird profile folders.
I suggest running a Microsoft Defender scan to make sure that you do not have this problem. Defender should detect this issue also when you try to open attachments. When you try to open infected attachments Thunderbird may come up with "not responding".
Some antivirus programs seem incapable of finding the Trojans Wacatac and Oneeva and others when they are embedded in email attachments.