Military mail, as opposed to civilian mail, refers to the postal services provided by armed forces that allow serving members to send and receive mail. Military mail systems are often subsidized to ensure that military mail does not cost the sender any more than normal domestic mail. In some cases, military personnel in a combat zone may post letters and packages to their home country free of charge. Modern military mail services are provided by most armed forces around the world. In some nations, individual service branches may run their own military mail program.