The following documents will provide you with a very good idea of what a cover letter (or a cover letter email) looks like.
The examples below indicate title, format, level & course code, and a short description.
Google Docs
Level 1
For example: 604-4P1
Scroll down to page two to view an instructor's comments on the student's work.
Google Docs
Levels 2 - 3
For example: 604-4P3
Scroll down to page two to view an instructor's comments on the student's work.