Flash sale sales letters create a sense of urgency and excitement among recipients. By offering limited-time discounts or promotions, these letters incentivize quick action, driving immediate sales. They tap into the psychological aspect of fear of missing out (FOMO), which encourages customers to make a purchase decision swiftly. Flash sale letters are particularly useful for clearing inventory, boosting revenue, and engaging customers who are looking for a great deal, making them a powerful tool in sales and marketing strategies.