number of people run their own Yes. A small number is a number. If we could go back in time and force every single implementer to follow every relevant RFC to

number of people run their own Yes. A small number is a number. If we could go back in time and force every single implementer to follow every relevant RFC to utter perfection (and make sure all the RFCs were perfectly unambiguous), I'd be more sympathetic. But email is fucked. The sheer number of oddball things, hacks, workarounds, deviations and other bits of mess that implementers have engaged in over the years means the RFCs should be treated as at best a loose hopeful outline of how email might in theory work.