If you set your profile to "show" your email, it does not allow your email address to be displayed on the board. What does happen is that the "email icon" appears at the bottom of all of your posts. If someone clicks on that icon, a dialogue box shows up which can be used to send you an email. Your addy is still not displayed; the email is just sent to you by UG. The email address of the sender will be displayed on that email.