Cursor settings are to do with your computer and whatever choices you set up and not Thunderbird. Typically a mouse cursor is usually an arrow which you use to point to eg: a button or item in menu or an email in a list of emails. Then a left click on the items you are pointing to performs the required function. If cursor changes to a hand with a pointing finger, then this means you are hovering over a link. That link maybe an image, or a piece of text or a button. If you hover over a 'link' then the real link data will display in the bottom Status bar, so you can check what you are clicking on before you click on it. If cursor changes to what looks like a capital letter I (with horizontal lines above and below) then it means you are hovering over a text box zone. This does not sounds like anything to do with Thunderbird. It sounds more like an issue with your computer. I've found this 'fist' issue reported in Linux Cinnamon and in Chromebook. Although it's not a Thunderbird issue, I did locate some info that might help. Internet search on this situation of fist cursor and not able to select stuff seems to occur in Chromebook. One person write this - assuming you are using a Chromebook - ''How to change from a fist to a regular cursor? It's easy. Here are these steps. And reply to me if they worked.'' ''1. Click on the time in the bottom right corner.'' ''2. Press the power button(it's the button next to "Sign out" and the lock button.'' ''3. The chromebook will shut down.'' ''4. Next, press and hold the refresh button on your keyboard. It's the button next to the right arrow and the square with the triangles.'' ''5. Then, press the power button on your keyboard.'' ''6. When the screen comes on that says "Chrome", with the chrome logo next to the Chrome wordmark, release the refresh button.'' ''7. Then log in.'' ''8. Try going on Play Store.'' ''Hope this works for you.'' Another person said the following but I've no idea what OS they were using.: ''My cursor randomly turned into a clenched fist so I pressed right click on the mouse and pressed reload it seems to have fixed it''