Can you see sunlight from the inside of your exterior door? If so, you may need to have the weather stripping repaired or replaced. Due to homes naturally settling over time, it's a good idea to stay on top of the upkeep & repairs to avoid air leakage, water intrusion & more. As you can see in the picture, sunlight can be seen in the seams of the door.
By repairing the weather stripping, it will allow the door to properly seal when closed and help prevent future possible damage.