Here's another mixed working that I photographed a couple of years ago, crossing the Langwies bridge on the Arosa branch in the winter. The RhB run quite a lot of mixed trains, particularly on the branch lines, but freight cars can turn up on the back of trains on the main Chur to Saint Moritz route, particularly for perishable goods and mail. Mail is carried in yellow containers as on this train.
Don Newing
Derbyshire, UK