I would create a "list file" with only those three individuals and set your restrict post to that list file. Delivery would occur to the entire list, but only those three would be able to post.
For the To: field question... are you asking that the sender address show up in the TO: field, or the individual recipient such that each person receiving the message will see his/her address in the To field?
From: firstname.lastname@example.org [mailto:email@example.com] On Behalf Of Daniel Kaliel
Sent: Monday, February 06, 2006 10:58 AM
Subject: list postings
I just wanted to verify something. I am creating a list that only 3 people can post to. All three are on the list, but the total list is 800 people. Is a moderated list the best way to ensure that only those 3 people can post to it?