If you are writing to someone who has a doctorate or medical degree, use the abbreviated form: "Dr." However, for other titles, such as professor, judge, rabbi, etc., write out the full title and capitalize it. For example, your salutation in a letter to a judge would be, "Dear Judge Barnard." Or, if your correspondence was with a rabbi, you might write, "Dear Rabbi Williams."
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.