The superintendent or other officer in charge of a patient shall, without reading the same, receive all letters addressed to the administrator, if so requested, and shall properly mail the same, and deliver to such patient all letters or other writings addressed to the patient. Letters written to the person so confined may be examined by the superintendent, and if, in the superintendent’s opinion, the delivery of such letters would be injurious to the person so confined, the superintendent shall return the letters to the writer with the superintendent’s reasons for not delivering them.