Some people prefers the keyboard shortcuts, while some prefer to do everything with the mouse. If you belong to the latter, you will find the new mouse gestures features in Gmail extremely useful.
To activate the mouse gestures feature, go to Settings->Labs. Scroll down to the mouse gestures section and check “Enabled“. Save the changes and you are set to go.
To navigate through the mails, simply right-click and do the following:
|Right-click and move the mouse right|
|Right-click and move the mouse left|
|Right-click and move the mouse up|