# certain crap mailers don't use standard headers to thread messages:
# http://madduck.net/blog/2009.05.20:read-notifications-standards-and-microsoft/
# this recreates at least the In-Reply-To header, but not the References list.
# Better than nothing.
:0
* ^Content-class: urn:content-classes:mdn$
* !^In-Reply-To:
*$ B ?? ^Original-Message-ID:$RE_EXTRACT_HEADER_VALUE
{
  LOG="attach-mdn:  unthreaded MDN in reply to $MATCH$NL"

  :0 fw
  |$FORMAIL -A "In-Reply-To: $MATCH"
}