I have a small screen and with this new version of Thunderbird there is not enough room on the screen to preview messages as the message display area is not able to be minimized beyond a certain point, unlike the earlier versions. The "double vertical arrow" appears but can't be dragged upwards beyond a certain point. So now I have to open each message in a new tab so that I can read it. Really tedious and frustrating! Tried to restore my computer to the earlier version of Thunderbird, but was not successful. Please alter this limitation in the next version upgrade. Thanks.