You can view your students' emails / Google Apps by visiting your PowerTeacher account.
Once you log in, look for the Student Info icon next to the class that you want to view:
Click the Email icon to view all your students' emails and demographics (contact info) for that class.
I want to mass email my class! What do I do?
Click the button on top that says "Email my whole class"
This will open up GMAIL and paste all your students' email addresses into an email as BCC.