Email is typically a desktop, keyboard and mouse activity. When Xerox needed to recreate email as a walk-up activity for multifunction machines with scanners, I was asked to lead the cross-functional team that set the original UI direction.
For email, we determined the most important task is addressing the email. Unlike copy, there was no paper source or output tray to choose. The form-field is typically filled in with the address of the machine or the logged in user's email. The subject can be set to a default. All image options were set to reasonable defaults.
Current versions of email are still based largely on the design my team developed.
The original design had to work with a 2-bit grayscale touch screen as it's interface.