The Wairarapa Mail was the only long-distance train to run out of NZR's Lambton Quay station, which primarily served commuter traffic from the Hutt Valley.
In 1936, railcars of the RM class Wairarapa type were introduced on the Wellington to Woodville route, and their ability to run over the Rimutaka Incline at speed allowed a quicker timetable.
[6] The Wairarapa Mail's demise was primarily due to the introduction of the railcars and would have likely come about sooner were it not for the traffic boom associated with World War II.
After the war, AB class locomotives were introduced in both the Hutt Valley and Wairarapa [4] and this modernised the train, but coal shortages in 1944 had led to the service's reduction to running thrice weekly.
[5] Despite the Mail's demise, carriage trains were sometimes operated to cater for demand at holiday times,[7] as the railcars could not run in multiple and there were only six of them.