During the Second World War, military personnel were granted the privilege to send first-class mail for free by Congressional act of March 27, 1942. Being a first-class mail piece, V-Mail met the requirements. Beginning on April 1, 1942, they could endorse letters on the upper right-hand corner with the word “FREE” and were supposed to include their name, rank, and designation of service in the left corner. See the 1st image for a free mail V-Mail and 2nd image for the civilian’s response.
Even though V-Mail was a system designed to make sending mail overseas faster and easier it did have its limitations. V-Mail advertisements made it clear that it was guaranteed airmail overseas but postage was particularly confusing to civilians because V-Mail had separate rates for different levels of service. Transportation was by airplane for the exchange between the V-Mail stations, but starting on May 15, 1944 one could pay more to have additional airmail service within the U.S. If a civilian wanted to send V-Mail using regular surface transportation in the U.S. they would pay three cents. But if a person in the U.S. wanted to expedite a letter to a V-Mail processing center, then she would pay extra for the airmail service (at first a 6-cent fee, later 8 cents). Any military service member wishing to have the extra airmail service for transport of V-Mail within the U.S. also had to pay the extra expense as well. See the 3rd, 4th, and 5th images for airmail V-Mail examples.