Because of the way email works, if you got it working, but screwed up (which is what would probably happen), you'd end up with a recreation of The Great Worm (Well, to be more accurate, you'd actually get a recreation of Bedlam-DL3: https://blogs.technet.microsoft.com/exchange/2004/04/08/me-t.... But it would have the same effect). Do you want to see what happens when millions of poorly configured email servers round the net scream out in agony?