Straighten the small metal catch at the top of the door that can become bent. Grasp it in your fingers and bend it back into shape. The catch is usually made of thin metal and is easy to bend. Open and close the door to make sure the mailbox latches properly.
Bend in the sides of the door. If the sides of the mailbox door have become bent and out of shape, use a chisel and your hands to gently reshape the sides back into position. They should be straight and not bend inward or outward.
Check the hinges and small screws underneath the door. Tighten if necessary and ensure the hinges are still functional.
Reshape the front of the door. If the door has become warped or misshapen, bend it back into its proper shape.