The Army Postal Service (APS) functions as a government-operated military mail system in India. A primary feature of APS systems is that normally they are subsidized to ensure that military mail posted between duty stations abroad and the home country (or vice versa) does not cost the sender any more than normal domestic mail traffic. In some cases, Indian military personnel in a combat zone may post letters and/or packages to the home country for free, while in others, senders located in a specific overseas area may send military mail to another military recipient, also located in the same overseas area, without charge. Officers are deputed primarily from the Indian Postal Service and from the Army Corps. APS is the only service that enables civil service officers to work in the armed forces.