S.D. Codified Laws § 58-33-53
Service of statement of charges, notices, and process in any such proceeding, action, or suit shall in addition to the manner provided in § 58-33-52 be valid if served upon any person within this state who on behalf of such insurer is:
and if a copy of such statement of charges, notices, or process is sent within ten days thereafter by registered or certified mail by or on behalf of the director to the defendant at the last known principal place of business of the defendant, and the defendant's receipt, or the receipt issued by the post office with which the letter is registered or certified, showing the name of the sender of the letter, the name and address of the person to whom the letter is addressed, and the affidavit of the person mailing the same showing a compliance herewith, are filed with the director in the case of any statement of charges or notices, or with the clerk of the court in which such action is pending in the case of any process, on or before the date the defendant is required to appear or within such further time as the court may allow.
SDCL 58-33-53