All notices given to an employer concerning a request for determination of insured status, a request for initiation of a claim series in a benefit year, a notice of unemployment, a certification for waiting-week credit, a claim for benefits, and any reconsideration of a determination must be made by United States mail or electronic mail. The employer may designate with the department its preferred method of notice. If an employer does not make a designation, then notices must be made by United States mail. The employer may not be required to respond to the notice until twelve business days after the postmark on notices sent via United States Mail or ten business days after the date a notice is sent via electronic mail.