There is mail in your mailbox six days a week so take time out of your day to thank the mail person who is responsible for getting it there! Thank A Mail Carrier Day is February 4th! In 1863, free city mail delivery started, and in 1896, free rural mail delivery began. Some people prefer to pick their mail up at the post office, for convenience or security reasons, and P.O. Boxes are lined up on the walls at the local post office. There is a fee for P.O. Box usage. In 1963, the Zip Code began.