What's the difference between cover letter and application email?
Write a traditional cover letter and attach it to your email. The committee reviewing your application may not get forwarded your original email. They will probably get a packet sent to them that's prepared by a staff member that aggregates all the submissions. Your email can be short and sweet: "Dear Whoever, Here are my application materials for the position Professor of Blah Blah Blah as advertised at URL. Please see attached for all the requested documentation."