Mac OS X El Capitan brings forth a couple of new features to help you better manage your emails. You can now delete or mark messages as read with some simple touch gestures. Here's how to use swipe gestures in the Mail app.
Touchpad Gestures for the Mail App
Open the Mail app and place the mouse cursor over the desired email.
Swipe two fingers to the left on the touchpad to display the Trash option, or swipe to the right to display the Mark as Read option.