Large, medium and small icon options in OS X’s Mail sidebar
If you’re running OS X Lion on your Mac, you have the ability to enlarge the icons in the sidebar of Mail and the Finder. This is particularly useful for those with less than stellar eyesight, or who simply have large LCD screens and want an easier target to hit when dragging files to or otherwise clicking the icons.
Changing the sidebar icons in Mail is actually not an option if you adjust the size of the Finder’s sidebar icons. Oddly enough, both are controlled in the System Preferences under the General icon. Simply choose the size you wish from the drop-down menu next to the Sidebar Icon Size item and both Mail and the Finder’s sidebar icons will immediately adjust accordingly.