On Tue, Sep 02, 2014 at 10:50:33AM -0400, Chris Siebenmann wrote:
> (This behavior is actually sometimes annoying, because it means that
> there is no clean standards-compliant way of saying 'this machine exists
> but you should never attempt mail delivery to it'. People often use
> various bogus MX values for this purpose, like 'MX localhost.' or 'MX
> .'.)
https://datatracker.ietf.org/doc/draft-ietf-appsawg-nullmx/
As of 2014/08/29 in the RFC Editor queue.
--
Viktor.