I was looking at a very quiet zoo day for email and our friends at outlook.com and india (eg scammy Microsoft) where abusing email dsn notifications.
We fixed it ala http://www.postfix.org/DSN_README.html
So I am happy*, email marketing professions not so, but if some of you abuse the clients this is what happens..
I suggest this expliot is worth fixing just to piss off all spammers (including marketing email experts).
*While the zoo’s postfix config does date in places from over ten years it is still good.