One of our clients was having problems with customers ordering in the UAE and not providing a PO Box address. This made it very difficult for them to send their packages, as they had to manually search for the PO BOX using the customers address, which is not ideal when you're getting orders every minute!
We put some code into the checkout that changed the address fields based on the countrys shipping address, then made the PO BOX compulsory. We forced those who wanted to ship to the UAE to leave their PO BOX and mobile number against an order. This completely solved the issue for the client. What’s more, we even added some validation to the box to prevent customers entering the incorrect format or dummy data.