MultiG is a Gmail notifier with the ability to monitor up to six Google accounts. It is a lightweight application that will place an icon in the system tray and will let you know whenever a new email arrives in your inbox by means of a notification sound and tooltips. If you double-click on this icon, the program will take you right to your Gmail account in your favorite Internet browser.
From the settings window you find when right-clicking on the tray icon, you will see a few options to configure the program. To add a new Gmail account you just need to enter your account information, that is, your username and password, and optionally your Google Apps account data. In this window you can also specify the time interval at which the program will check your accounts and choose any WAV sound for the notification. Additional options allow you to start the application on Windows starup, change the colors of the tray icon, and choose your favorite browser.
The application is really easy to set up and during my test, it did let me know about new emails via tooltips. However I think the notification system it uses is quite limited. You need to hover the mouse over the icon to see if there are new emails, the app won't actually display pop-up messages, which would be more efficient for that matter, in my opinion. On the other hand, the alert sound did not seem to be working.
In short, there are lots of alternatives here on Software Informer, many of them free and with more features, so be sure to explore the site before you decide to buy this app.