The "Bahnpostwagen" m - a/26 was arranged for the transport of all kind of mails. In it, mailings (letters, parcels and parcels) were processed before and during the journey. The use of these wagons was mainly due to the night hours because the bulk of the mailings were to be delivered by the senders in the afternoons or evenings to reach the place of destination in the next morning . The transport took place in so-called postal trains, D- and E-trains or other trains of the German Federal Railroad.
As seen from the outside, the railway mailing car consists of the drive and the car body, which in turn consists of the undercarriage, the front and side walls and the car roof. From the 1967 series, the head section is prepared at both ends of the underframe for the later installation of a central buffer coupling and for the resulting central introduction of the compressive forces.
A mailroom, a locker room and a packing room are housed as workrooms in a railroad car of the type a. The necessary equipment for the personal needs of the car crew, wardrobe, laundry and a train toilet are located in the anteroom at the wagon end of the letter room. In the mailroom, work desks (750 mm deep, 833 mm above floor level) are arranged on the side walls and on the front wall, and letter dividers with six or seven rows of panels are arranged on them. In the upper, overlapping sections the floors consist of strong clear glass plates so that the complete emptying of the compartments can be easily checked. To the left of the end wall shed is a pivotable truss, which can be fixed at any angle. A mailbox is inserted into each side of the facades at the side walls, which is to be fed from the outside through an insertion slot with closure flap. In front of the sorting tables can be attached at any place letter-box boxes, in which the not yet distributed letters are ready to hand.
source: [DE] Wikipedia