I asked this question about 115.4.1 and was told to try in safe mode. However I cannot connect to my mail servers of which I have 2 and Gmail when in safe mode. Please look into the resource handling problem with the new Thunderbird under Win10. 1) Whenever I open Thunderbird the Gmail messages apparently get refreshed taking several minutes. I have cleaned up that inbox and limited to 366 days of mail. 2) I spent hours moving mail from past year from my other accounts into local storage. You no longer can scroll and block select more than about 20-30 messages at a time regardless of the background activity 1) above. The program requires you to repeatedly release shift key to grab more than a few messages. If you are able to grab say 1000 messages, and try to move them, the system chokes and does not respond. 3) Any background activity impedes the ability to scroll the inbox. The new versions are crippled in some way as far as resources. The older version was more tolerant. Please listen to complaints. Putting in safe mode I cannot troubleshoot. It is also very difficult in Win10 to follow instructions to safe mode unlike previous OS.