How is your friend sending them? Normal way is to place address of first recipient in the "To" window and all others in the "CC" window If you want everyone on the list to see all the other email addresses.
If you want to send one email to several different people but not show each persons address then as above but instead of using the "CC" window, use the "BCC" window.
CC = Carbon copy. BCC = Blind carbon copy.