#!/bin/sh
set -e
folder -create +dupl-demo                                                
list_id='list.example.com'
message_id='a.%d@example.org'

for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20; do
  if test $(($i%4)) -eq 0; then
    the_list_id="$list_id"
  else
    the_list_id=
  fi
  the_message_id="$(printf "$message_id" $(($i%5)))"
  printf 'Subject: %s\nList-Id: %s\nMessage-Id: %s\n' \
    "$the_list_id/$the_message_id" "$the_list_id" "$the_message_id" > "$(mhpath +dupl-demo new)"
done
rmm +dupl-demo $(dupl)
scan +dupl-demo