Introduce yourself in the first paragraph (if necessary). Also include why you're writing, and how you found that person's Email address, or the opportunity you're writing about. Ex.
My name is Earl Rivers. I'm contacting you to apply for the administrative assistant position listed on CareerXYZ.com.
My name is Arlene Rivers. I am writing about the traffic citation I received on December 31, 2009. I obtained your Email address from the Westchester County Clerk website.