In any suit for annulment, for divorce, either a vinculo matrimonii or a mensa et thoro, or for affirmance of a marriage, an affidavit shall be filed that the defendant is not a resident of the Commonwealth of Virginia, or that diligence has been used by or on behalf of the plaintiff to ascertain in what county or city such defendant is, without effect, an order of publication shall be entered against such defendant by the court, or by the clerk of the court wherein such suit is pending, either in term time or vacation, which order shall state the object of the suit and the grounds thereof, and the order of publication shall be published as required by law. If the plaintiff in the suit has been determined to be indigent by the court pursuant to § 19.2-159, the order stating the object of the suit and the grounds thereof shall be mailed to the defendant at his last known address and posted on the main entrance to the circuit courthouse of the city or county wherein the suit is filed, and no order of publication shall be required. No depositions in the suit shall be commenced until at least 10 days shall have elapsed after the order has been duly published or mailed and posted as required by law. All annulments or divorces heretofore granted in suits in which the defendant was proceeded against by an order of publication or of mailing and posting which required the defendant to appear within 10 days after due publication or mailing and posting thereof, and in which depositions were taken less than 15 days, but not less than 10 days, after such due publication or mailing and posting and in suits in which the defendant was proceeded against by an order of publication or of mailing and posting issued on an affidavit that diligence had been used by or on behalf of the plaintiff to ascertain in what county or city such defendant was, without effect, or wherein the order of publication or of mailing and posting was entered by the court, are hereby validated and declared to be binding upon the parties to such suit, when the other proceedings therein were regular and the annulment or divorce otherwise valid. The cost of such publication or of such mailing and posting shall be paid by the petitioner or applicant.