Tenn. Code Ann. § 8-4-203: Service of subpoena

Service of such subpoena shall be had by a designated representative of the comptroller of the treasury either handing a copy of the subpoena to such witness, at which time service is complete; mailing a copy of the subpoena to such witness by certified mail, return receipt requested, in which case service shall be complete on the date the witness signs the certified mail receipt; or, if the witness cannot be found, mailing a copy of the subpoena to the last known address of the witness by first-class mail, in which case service shall be complete upon mailing. Such process shall run throughout the state.