GNOME, by default, has a notification area which includes an applet that informs users of any system updates, changes, or events. This includes the arrival of email messages on Evolution. You can refer to this built-in feature of GNOME for any email notifications.

In GNOME version 2 you may modify the notification area and set it up to become a system tray by using external software such as Alltray that might be available for installation in the software management tool of your distribution. This is not possible in GNOME 3 anymore.