A notice of cancellation or nonrenewal of health insurance coverage by an insurer due to nonpayment of premiums shall be in writing, shall be delivered to the named policyholder or mailed to the named policyholder at the last known address of the named policyholder, shall state the effective date of the cancellation or nonrenewal and shall be accompanied by a written explanation of the specific reasons for the cancellation or nonrenewal. Proof of mailing of such cancellation or nonrenewal notice shall be retained by the insurer for a period of not less than 1 year. This section shall not apply to any policy issued under the Delaware Healthy Children Program or any long-term care policy where notice provisions regarding cancellations or nonrenewals are specifically addressed elsewhere in this title or in regulations promulgated thereunder.