If you are using address labels, make sure your labels are on straight. Mail processing machines have trouble reading crooked or slanted information.
Military Mail – Military addresses must show the full name with middle name or initial and the PSC number, unit number, or ship name. Replace the city name with APO, FOP or DPO, and the state with AA, AE, or AP, and include the ZIP+4 code.
Print the delivery and return addresses on the same side of your envelope or card. The addresses should be written parallel to the longest side. Print or type your address in the upper left corner on the front of the envelope.
Letters, bills, greeting cards, and other documents can be sent in standard white, manila, or recycled paper envelopes. These envelopes, along with stationery and prepaid First-Class Mail postcards and envelopes, can be purchased at the Post Office.