There is a tendency to think that the often arbitrary rules of letter writing don’t really matter, that as long as your recipient can work out what you’re saying, that’s good enough. This shows a great deal of disrespect for your recipient, though, and for your own ideas. It suggests that a) your reader’s time isn’t valuable enough for you to write clearly and efficiently, and b) that you don’t particularly care about the content of your letter.
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.