houston.rr.com MX fubar?

Mon Jan 14 01:10:58 UTC 2008

On Jan 13, 2008 9:55 PM, Tony Finch <dot at 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