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."
Writing for a business audience is usually quite different than writing in the humanities, social sciences, or other academic disciplines. Business writing strives to be crisp and succinct rather than evocative or creative; it stresses specificity and accuracy. This distinction does not make business writing superior or inferior to other styles. Rather, it reflects the unique purpose and considerations involved when writing in a business context.