Say something positive in the subject line. It can be as simple as a small, handwritten thank you note of thanks.Thank you for being a valued member of our community. Subject: Thank You for Referring New Customers! Please accept my gratitude and appreciation. Thank you for your time. Thank you so much for purchasing our 8person tent. We love it when new customers give us a chance and your purchase means the world to us. - Example: "I want to take a moment to express my sincere gratitude for your hard work and dedication. Start with "thank you".