Section 12. Within three months after the allowance of a will and the appointment and qualification of an executor, it shall be the duty of the executor to notify by mail the devisees and legatees named in the will whose addresses are known to him that devises, legacies or bequests have been made to them and to file in the probate court an affidavit showing the names of those notified and the addresses to which notices were mailed. In case an administrator with the will annexed is appointed he shall have the same duty unless it has already been performed by an executor.