In Bibb County, the sheriff shall execute every order from every court in Bibb County to subpoena witnesses as provided in Section 12-21-180, or the service may be made by first class mail as follows: It shall be the duty of the sheriff of the county to enclose the subpoenas in an envelope addressed to the person to be served and place all necessary postage and a return address thereon. In the event the witness subpoena is returned to the sheriff by the post office department of the United States without delivery, the subpoena shall be by the sheriff returned NOT FOUND. All witness subpoenas not returned to the sheriff by the post office department shall be considered for all purposes as sufficient personal and legal service. It is specifically provided, however, that, if the party calling a witness expressly requests in writing that the subpoena be delivered to such witness personally by the sheriff or one of his or her deputies in person, such witness shall be so served. The provisions of this section in reference to service by mail shall not apply, however, to witness subpoenas returnable before the court instanter. Such subpoenas shall be served only a provided in Section 12-21-180.