E-mail is the preferred method for most business (and personal) communication because it is quick, efficient, easy to archive, and easy to search.
You write to the coordinator of the writing center to apply for a job as a tutor, courtesy copying the message to a professor who has agreed to serve as a reference.
You send an e-mail to classmates in a writing class, looking for someone to collaborate on a Web project.
You e-mail the entire College of Liberal Arts faculty to invite them to attend a student production of Chekhov’s Uncle Vanya.
You e-mail a complaint to your cable supplier because a premium sports channel you subscribe to has been unavailable for a week.