MID_CACHE_FILE = $PMVAR/msgid.cache

LOCKFILE = $MID_CACHE_FILE$LOCKEXT
:0
*$ !SKIP_DUP ?? .
*$ !$MSG_DEJAVU
* ^Message-ID:
* ? $FORMAIL -D 16384 $MID_CACHE_FILE
{
  LOG="duplicate:   drop duplicate message $MSGID$NL"
  LOCKFILE   # unlock
  SWITCHRC=$PMDIR/discard
}
LOCKFILE   # unlock