mine is setup w hen i send a mass email to all the members it shows my email addy i added to it, as far as when they sign up, i dont think it does, i think it shows you have signed up with so and so through forumotion.com forums, blah blah blah click here to activate..
as far as sending mass emails from the admin panel you can change that to work with your own email

activation registration email, i dont see the point of having it tho