The summons shall be served in the manner provided by law for the service of summons in other civil actions in the district court, except as otherwise herein provided. The summons shall be served upon all persons who are not residents of the state and upon those designated as "all other persons or parties unknown claiming any right, title, estate, lien, or interest in the lands described in the complaint herein" by publication for three consecutive weeks in a qualified legal newspaper published in the county in which the action is pending; provided, that personal service without the state may be made on any nonresident defendant in the manner provided by law. No affidavit of nonresidence, notice of lis pendens, or sheriff's return need be filed before the commencement of the publication or before the making of personal service without the state. At least 20 days before the trial of action, the attorney for the plaintiff shall mail a copy of the summons to each nonresident defendant whose post office address has been ascertained by diligent search and inquiry, of which the affidavit of the attorney, filed with the court administrator, shall be conclusive evidence. The return of the sheriff stating inability to find any defendant within the county and that such defendant cannot be found therein after diligent search, together with the affidavit of plaintiff's attorney stating the belief that such defendant is not a resident of the state, filed with the court administrator at any time before the trial, shall be prima facie evidence that the facts therein stated are true and that such defendant is not a resident of the state.