Most similar e-mail utilities use a sound to notify the user. This one an do that and/or notify via an attention-getting graphical pop-up. My sound is normally muted or disabled on my workstations to avoid distracting annoyances. This feature is invaluable for me. ;)

Super small email checker

Poppy is a neat mail checker....not glitzy but it works and has enough functionality for me...I like it a lot.