Such order shall be published in some newspaper published and circulated in the county, or in such other paper as the court may direct, at least once in each week for 2 successive weeks immediately preceding the day set for the hearing, and a copy of such order shall be mailed to each absent or non-resident person having a last known postoffice address, by registered mail, and a return receipt demanded. Proof by affidavit shall be made of such mailing, and whether or not a return receipt was received, and if one was received, it shall be attached to said affidavit; but such publication and mailing shall not be necessary in any case in which a copy of such order has been served personally or by registered mail on each such absent or non-resident person.