Trivia: Hitchcock had two cameo appearances in the movie Suspicion: the first takes place right after the opening scene where Johnnie and Lina meet on the train, when Johnnie and friends are gathered for a 'photo op' just prior to the start of the 'hunt'. You see Hitchcock shortly after that scene walking with a horse past the camera. He is to the left of the horse and is wearing a cap and light colored jacket. The second cameo shows Hitchcock, albeit from a distance and not easily identifiable and ever so briefly, posting a letter at a mailbox in town.
Trivia: Alfred Hitchcock's cameo occurs about 47 minutes into the movie. When Mrs Newsham parks her car outside the post office, Hitchcock can be seen putting a letter into the postbox.