A policy in which the insurer reserves the right to refuse renewal shall have the following clause at the beginning of the provision in § 58-17-17,
"Unless not less than thirty days prior to the premium due date the insurer has delivered to the insured or has mailed to his last address as shown by the records of the insurer written notice of its intention not to renew this policy beyond the period for which the premium has been accepted."
SDCL 58-17-18