We got all these letters back!! ...and we weren't supposed to When we send thousands of letters through the postal service every month, we know there's a chance some of them won't reach their destination. So each week we check our PO box for returned letters. With each returned letter, we contact the customer and verify the address on the envelope. Sometimes the problem is as simple as a typo in the address, while other times there doesn't seem to be any issue with the information they gave us.