If you have the latest updates for Windows 8.1 you should have the close (x) functionality on full screen apps such as mail. You can also pin full screen apps to the taskbar, just right click on the mail icon on your start screen and choose pin to taskbar
If you have the latest updates for Windows 8.1 you should have the close (x) functionality on full screen apps such as mail. You can also pin full screen apps to the taskbar, just right click on the mail icon on your start screen and choose pin to taskbar