#Thunderbird - Please include folder/thread pane formatting (font type, font size, row height, space between rows, font colour, background colour) in Settings. The default settings a very user unfriendly and many don't have the IT skills to fiddle with css (I don't even know what it is...)
Also allow a rearrangement of the order of folders within an account without having to get an add-on (which may become unusable anyway as new TB updates are rolled out).