Thunderbird on my top of the range Win11 laptop was working perfectly until it self-updated to 115.10.1 a couple of days ago. Accessing messages already in the various folder is fast as usual. Unfortunately anything like deleting, downloading a new message is excruciatingly slow : several seconds to click and delete in the inbox. Several seconds to access a message just downloaded. The first time it happened I had a whole bunch of messages deleted because the I kept clicking when I saw no action. It seems to me like it has problem updating the messages in the inbox. Very painful for something that was working so well.