When your letter is to more than one person, write out all of their names separately, separating them with commas. For example, "Dear Mr. Hobbes, Ms. Luxe, and Mr. Hopman." For married couples, if one person in the couple has changed his or her name, you only need to use the last name once. For instance, "Dear Mr. and Mrs. Smith."
Parts of a Business Letter. Business Letter is a letter which is used by organizations to communicate in a professional way with customers, other companies, clients, shareholders, investors, etc. Business letter uses formal language and a specific format.