 The term "M-bag" is not expanded in USPS publications; M-bags are simply defined as "direct sacks of printed matter ... sent to a single foreign addressee at a single address"; however, the term is sometimes referred to informally as "media bag", as the bag can also contain "discs, tapes, and cassettes", in addition to books, for which the usual umbrella term is "media"; some also refer to them as "mail bags".Military mail is billed at domestic rates when being sent from the United States to a military outpost, and is free when sent by deployed military personnel.The overseas logistics are handled by the Military Postal Service Agency in the Department of Defense.