This book shelf contains APO/FPO resources. APO/FPO supports mail delivery for military facilities overseas and to deployed personnel in combat zones worldwide. Most services, such as Certified Mail, registered mail, delivery confirmation, insured mail, certificate of mailing, return receipt, restricted delivery and return receipt for merchandise were available to the APO/FPO. Mail sent from one Army post office (APO) to another APO can be sent for free as inner- or intra-theater delivery service (IDS) as long as it does not transit the United States.