On Thu, Jul 17, 2014 at 06:06:42PM -0700, Dave Crocker wrote:
It just designates non-sending domains,
No, it designates non-/receiving/ domains:
That's a bit of an under-statement, because, for example,
with the widely practived:
reject_unknown_sender_domain
restriction in Postfix, mail from nullmx domains *is* rejected,
so any that declare-themselves non-receiving become non-sending
in practice. If the draft suggests that nullmx domains might
expect to send mail will impunity, that would be misleading.
In practical terms, if you don't receive, you can't send (that is
you can't use the domain in the SMTP return path).
--
Viktor.