Tenn. Code Ann. § 48-55-104: Service on corporation

(a) A corporation's registered agent is the corporation's agent for service of process, notice, or demand required or permitted by law to be served on the corporation.

(b) Whenever a domestic or foreign corporation authorized to transact business or conduct affairs in this state fails to appoint or maintain a registered agent in this state, whenever its registered agent cannot be found with reasonable diligence, whenever a foreign corporation shall transact business or conduct affairs in this state without first procuring a certificate of authority to do so from the secretary of state, or whenever the certificate of authority of a foreign corporation shall have been withdrawn or revoked, then the secretary of state shall be an agent of such corporation upon whom any such process, notice, or demand may be served.

(c) This section does not prescribe the only means, or necessarily the required means, of serving a corporation.