Having a notification when new email arrives can be nice and really useful if you're waiting for an important message. But if you're using a desktop email client or maybe a third party webmail service, you might not want to run a big client application or have to keep checking that tab in Firefox to see if new mail has arrived. Mail Notification is a small application that can run in your system tray area on GNOME (but it also runs fine on KDE, Xfce or pretty much any other desktop environment) that sits there and checks your account(s) for new email.