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