Verifique se notifique ,
If you access your email in a browser, you'll love Notify. Notify is an awesome email notifier for Mac OS X. It fits seamlessly into your menubar, only vying for your attention when you have new mail. Notify supports mutliple accounts, including Gmail/Google Apps, MobileMe, and Rackspace Email. All in a beautiful interface.
Veja também Top 10 Grandes Notificadores do Gmail para Windows e Mac .
Existe um Notificador do Gmail de Google também.