Looks like there’s a lot of broken systems out there then 
I see mails with X-Auto-Response-Suppress: All (from exhange)
Some just have:
Content-Type: multipart/report; report-type=delivery-status;
boundary="110e4b6c-159b-4262-b2ca-cbe359515e6a"
as content type (and no other identifying headers)
QMail just sends a reject mail from From: MAILER-DAEMON@somedomain or From: mailer-daemon@somedomain.
Another one: X-QQ-HolidayReply: true
(I setup a sieve filter to block mailer-daemon & postmaster locally which cuts down 99% of these btw)