Re: houston.rr.com MX fubar?

["Suresh Ramasubramanian" <ops.lists () gmail com>]

On Jan 13, 2008 9:55 PM, Tony Finch <dot () dotat at> wrote:
> On Sun, 13 Jan 2008, Suresh Ramasubramanian wrote:
> > One operationally better way to go seems to be Mark Delany's mx0dot
> > proposal, which started out as an internet draft, but seems to have
> > lost momentum .. the concept is sound though.
>
> Exim implements this convention.

Er, the concept is DNS related .. totally MTA independent.  Simply
declaring that there is no MX record in a way that stops fallback to
an A record.

Exim would check for such.  Other MTAs, even those that dont
explicitly check for it, would try to deliver email and fail
immediately, creating a 550 / NDN / whatever.

Basically -

> To indicate that a domain never accepts email, it advertises a solitary MX RR with a RDATA section consisting of an 
> arbitrary preference number 0, and a dot terminated null string as the mail exchanger domain, to denote that there 
> exists no mail exchanger for a domain.
>
> The dot termination denotes that the null MX domain is considered to be absolute, and not relative to the origin of 
> the zone, the behavior of dot termination and the formatting of this record is as described in STD13

--srs