Mass. Gen. Laws ch. 190B § 2-515
A will may be deposited by the testator or the testator's agent with any court for safekeeping, under rules of the court. The will shall be sealed and kept confidential. During the testator's lifetime, a deposited will shall be delivered only to the testator or to a person authorized in writing signed by the testator to receive the will. A guardian of the estate or conservator may be allowed to examine a deposited will of a protected testator under procedures designed to maintain the confidential character of the document to the extent possible, and to ensure that it will be resealed and kept on deposit after the examination. Upon being informed of the testator's death, the court shall notify any person designated to receive the will and deliver it to that person on request; or the court may deliver the will to the appropriate court.
Mass. Gen. Laws ch. 190B, § 2-515