[Mailman-Users] setting "nomail" by default?

[Rod Neep]

Is it possible (in 2.1.1) to set up one of my lists so that all 
subscribers by default have their "nomail" flag set to not to receive 
mail?

I appreciate that this may at first appear to be silly, but I want to 
set up one of my lists to:

a. allow people to post messages, but not see each others' posts

b. have the system send an auto response, saying that we will deal
    with their query as soon as possible (we can do that in Mailman)

c. then one of our (several) staff reply to the query
    (i)  to the individual
    (ii) cc to the list so that *we* see when it has been dealt
         with by one of our team.

i.e. *we* receive mail posted to the list, but normal users don't.

Thanks
Rod