If your intent is to persuade the recipient in some way, whether it's to invest money, give you a reference, hire you, partner with you, or fix an issue, create a compelling case for your cause. If, for example, you want the reader to sponsor a charity event, identify any overlap with their company’s philanthropic goals. Convince the reader that helping you would be mutually beneficial, and you will increase your chances of winning their support. Keep your closing paragraph to two sentences. Simply reiterate your reason for writing and thank the reader for considering your request.
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."