No, LISTSERV cannot  just force userid@node in the from  field in that case.
It calls  the RFC822 parser to  get info from  the header and the  parser says
"Sorry, this is just  no valid RFC822 mail". And it is indeed  not -- it's IBM
NOTE sent as  MAIL. If it's not  a valid RFC822 mailfile, it  can be anything,
X.400 mail,  local homebrew mail,  or just a  standard file which  happened to
have a filetype of mail.
 
  Alan: you cannot set the default option  to NOFILES, but you can issue a SET
listname NOFILES FOR userid@node as they subscribe.
 
  Eric