Enable Automatic E-mail Check and Desktop Notifications

Login to your webmail and click the 
 icon on the top left (Figure 1):
Figure 1
 
Under the General section, click on the Refresh View drop-down (Figure 2).
Figure 2
On the resultant menu, select how often you would like the browser to automatically refresh and check for new e-mail (Figure 3).
Figure 3
Place a checkmark on the Enable Desktop Notifications checkbox field (Figure 4).
Figure 4
Click the save button on the upper-right of your screen to save your changes (Figure 5).
Figure 5