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."
The Best Formatting for a Business Letter. A business letter is a formal document often sent from one company to another or from a company to its clients, employees, and stakeholders, for example. Business letters are used for professional correspondence between individuals, as well. Although email has taken over as the most common form of correspondence, printed out business letters are still used for many important, serious types of correspondence, including reference letters, employment verification, job offers, and more.