SDCL § 15-7-11: Proof of service on nonresident or absent aircraft operator.

Proof of the service as provided by § 15-7-10 must be attached to the original process. If the service is completed by mailing, such proof must include showing by affidavit that the address to which the copies were mailed was in fact the last known post office address of the defendant which the plaintiff could, with reasonable diligence, ascertain and must include also the registry or certified receipt issued by the postal authorities.