D. Except as otherwise provided herein, any written notice required in this section may be mailed by registered, certified, first class, or air mail at the sender's option. Proof of receipt by the extender of credit may consist of a return receipt executed by an employee of the extender of credit. Proof of receipt by the consumer may be a return receipt executed by the consumer. Proof of mailing any written notice may be a postmarked registered mail receipt, a postmarked certified mail receipt, or a post office certificate of mailing.
The written notice shall identify the contract, state the names of the extender of credit and the consumer, and shall include the date and a reasonable description of the violation.
In any case where the extender of credit must respond in writing to a complaining consumer, the written notice or other required written response shall be mailed to the last address contained in the extender of credit's file on that consumer, unless the consumer specifies a different address in his written notice sent to the extender of credit.