Chris,
Sounds like what you need is the DISTRIBUTE feature of LISTSERV.  You build
your file, put the list of users it is to go to at the beginning with a few
control cards, and send it to the nearest LISTSERV.  This LISTSERV sends
it to anyone close to it, and forwards copys to other LISTSERVs with lists
of users there.  Each of these LISTSERVs also sends to local and close by
users, and forwards copys to other LISTSERVs, until the file has been
transmitted to everyone on the list.  For more information, send the commands
     INFO DIST and INFO JOB
to your nearest FRECP11 listserv.
 
For more information, drop me a line direct.
 
Harold