Indiana Code Title 34. Civil Law and Procedure § 34-33-3-3

Sec. 3. If a defendant refuses to accept or claim registered mail, the secretary of state shall return the registered mail to the plaintiff or to the plaintiff's attorney. The mail shall be appended to the original process, together with an affidavit of the plaintiff or of the attorney or agent that the summons was delivered to the secretary of state in accordance with Trial Rule 4.10 of the Indiana Rules of Trial Procedure, together with the fee set forth in IC 23-0.5-9-56, and was returned unclaimed by the United States Postal Service. The affidavit, together with the returned envelope including the summons, is considered sufficient service upon the defendant.