To Setup on Windows:

1. Download and install the Google Notifier
2. Right click the Google Notifier icon in your system tray (lower right, near the clock) and select Options
3. Select the Gmail tab and check the box next to Use Gmail for internet mailto: links
4. Click Ok
5. All done!

To Setup on Mac:

1. Download and install the Google Notifier
2. After it’s been installed and run click the Mail icon in the Menu bar and select Preferences
3. Select the Gmail tab and click Enable Gmail notification
4. Use the drop-down box next to Compose mail in: to select Gmail
5. Close out of this window
6. All done!