Section 39. The return day of said notice shall be not less than twenty nor more than sixty days after the date of issue. The court shall also, within seven days after publication of said notice in a newspaper, cause a copy thereof to be sent by the recorder by mailing a registered letter to every person named therein whose address is known. The court shall also cause a duly attested copy of the notice to be posted in a conspicuous place on each parcel of land included in the complaint, by a sheriff or deputy sheriff, fourteen days at least before the return day thereof, and his return shall be conclusive proof of such service. If the plaintiff requests to have the line of a public way determined, the court shall order notice to be given by the recorder, by mailing a registered letter to the mayor of the city or to one of the selectmen of the town or towns where the land lies, or, if the way is a highway, to one of the county commissioners of the county or counties where the land lies. If the land borders on a river, navigable stream or shore, or on an arm of the sea where a river or harbor line has been established, or on a great pond, or if it otherwise appears from the complaint or the proceedings that the commonwealth may have a claim adverse to that of the plaintiff, notice shall be given in the same manner to the attorney general. The court may also cause other or further notice of the complaint to be given. The court shall, so far as it considers it possible, require proof of actual notice to all adjoining owners and to all persons who appear to have any interest in or claim to the land included in the complaint. Notice to such persons by mail shall be by registered letter. The certificate of the recorder that he has served the notice as directed by the court, by publishing or mailing, shall be filed in the case before the return day, and shall be conclusive proof of such service.