You have  to use an exit  for that. I'm  not sure I fully  understand the
problem - you said  F=PUNCH rather than F=MAIL, and I  would think that a
BITNET  user who  explicitly codes  F=PUNCH when  he has  the ability  to
receive Netdata files gets what he deserves. I realize there is presently
no convenient way to prevent mail-only  users from AFD'ing to files which
cannot be  sent via mail,  but I have  found no satisfactory  solution to
this problem so far.
 
  Eric