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.
Quick Tip: Don't use your work email address for job searching. Use your personal email account, or set up a unique account to use just for your job hunt. Many free online email services exist, like Gmail and Yahoo mail, that you can use to set up a new email account exclusively for your job search.