A notice of cancellation or nonrenewal of group health insurance coverage by an insurer due to nonpayment of premiums shall be in writing, shall be delivered to the policyholder or mailed to the policyholder at the last known address of the 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 long-term care policy where notice provisions regarding cancellations or nonrenewals are specifically addressed elsewhere in this title or in regulations promulgated thereunder.