LISTSERV is designed to give the smallest number of copies that it can
going out over the network, to cut down on bandwidth.  You're always going
to get multiple copies of mail in your spool if you have more than one
recipient there, whether you're talking mailing lists or someone on your host
sending five people there identical pieces of mail.
 
The other way you could do this is to use one of the VM Usenet News
implementations.  The problem here, of course, is that while you only have one
copy of each article, you carry EVERY article, whether or not anyone on your
site reads it or not.  I can state from experience that this definately takes
up more space (although not in the spool) than the multiple copies of LISTSERV
mailings.
 
Paul Goodwin
Georgia Institute of Technology