In article
<20140718032611(_dot_)7B87E1A7B838(_at_)rock(_dot_)dv(_dot_)isc(_dot_)org> you
write:
There are lots of machines which do not have the SMTP port configured
yet have A or AAAA records resulting in a implicit MX record and
week+ long no delivery notifications.
Right. That's exactly, precisely, the problem that null MX is
intended to address.
The alternative to this is to remove the implicit MX record
construction from SMTP and make the presence of MX records mandatory
for SMTP. I'm sure there will be many more complaints about doing
that than adding a explicit no service record.
That would be fine with me, but I hear it's 30 years too late, even for IPv6.
R's,
John