Open Control Panel > Sound.
Sound settings window >Sounds tab.
Select Windows Default in the Sound Scheme drop-down menu.
Scroll down the list in the Program Events box and select Desktop Mail Notification.
Click on that drop-down menu and select the sound from the list. After selecting a sound, click on the Test button to hear it.
Click Apply.
Now, scroll down the list in the Program Events box and select New Mail Notification.
Repeat [Click on that drop-down menu and select the sound from the list. After selecting a sound, click on the Test button to hear it.
Click Apply.]
Click OK to save the changes.