Tennessee Code Title 56. Insurance § 56-2-603

(a) The service of process shall be made by delivering to and leaving with the commissioner or some person in apparent charge of the commissioner's office two (2) copies of the service of process and the payment to the commissioner or other person of the fees prescribed by law.

(b) The commissioner shall forthwith mail by registered mail one (1) of the copies of the process to the defendant at its last known principal place of business, and shall keep a record of all process so served upon the commissioner.

(c) The service of process is sufficient; provided, that notice of the service and a copy of the process are sent within ten (10) days thereafter by registered mail by plaintiff or plaintiff's attorney to the defendant at its last known principal place of business, and the defendant's receipt, or receipt issued by the post office with which the letter is registered, showing the name of the sender of the letter and the name and address of the person to whom the letter is addressed, and the affidavit of the plaintiff or plaintiff's attorney showing a compliance with this section are filed with the clerk of the court in which the action is pending on or before the date the defendant is required to appear, or within a further time that the court allows.