Tenn. Code § 20-2-216
The original process, endorsed as described in this section, an affidavit of the secretary of state setting forth the secretary of state's compliance with the requirements of § 20-2-215, and the return receipt signed by, or duly in behalf of, the defendant, shall be attached together and sent to and filed by the clerk. There shall be endorsed on the original process by the secretary of state over the secretary of state's signature the date the secretary of state mailed the certified copy to the defendant and the date on which the secretary of state received the return receipt of the defendant. Thereupon, service on the defendant shall be consummate. An act of a deputy or regular assistant of the secretary of state in the secretary of state's behalf shall be deemed the equivalent of the act of the secretary of state.
T.C.A. § 20-2-216