On 7/18/2014 4:58 AM, John C Klensin wrote: > I believe (in agreement with what this document > just about says) that this mechanism is a back-door workaround > to requiring MX records for any host that is willing to accept > incoming email. It says and implies no such thing. Nor does it move us towards that. Suggesting otherwise sounds odd, given that you say you don't object to the mechanism. The document formalizes an existing practice. We sometimes do that in the IETF. d/ -- Dave Crocker Brandenburg InternetWorking bbiw.net