Learn what letters to clients are, review tips to help you write them and follow these templates when crafting engaging client letters. 1. Use a professional letterhead.The business letter will be a representation of your company. Learn when and how to write a thank you letter to your customers and review a template and two examples to help you craft your own letter. Wondering how to write a business email? Get prospects' attention and drive them through the sales process with these email templates. Writing a dear valued customer letter. This client template can be used for good customer service and shows the meaning of valued customers. These customer service email examples, best practices and tips will help you to exceed your customer's expectations. Want to improve your customer service letters?