Mass. Gen. Laws ch. 190B § 3-102
Except as provided in section 3-1201, to be effective to prove the transfer of any property or to nominate an executor, a will shall be declared to be valid by an order of informal probate by a magistrate or an adjudication of probate by the court, except that a duly executed and unrevoked will which has not been probated may be admitted as evidence of a devise if (1) no court proceeding concerning the succession or administration of the estate has occurred, and (2) either the devisee or the devisee's successors and assigns possessed the property devised in accordance with the provisions of the will, or the property devised was not possessed or claimed by anyone by virtue of the decedent's title during the time period for testacy proceedings.
Mass. Gen. Laws ch. 190B, § 3-102