[ietf-dkim] Re: Comment about SSP Draft - MX lookup requirement

[Stephane Bortzmeyer]

On Thu, Nov 01, 2007 at 12:57:31PM -0400,
 Wietse Venema <wietse at porcupine.org> wrote 
 a message of 38 lines which said:

> As long as something exists, the result of MX lookup will be "no
> data" or an MX record, but it won't be NXDOMAIN.

Perfectly right but one should note that some broken DNS servers reply
with NXDOMAIN when they should not. Yes, they are completely broken
but they exist.

Example:

% dig MX ns.yp.to

; <<>> DiG 9.3.4 <<>> MX ns.yp.to
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 59696
                 
NXDOMAIN but the domain exists:

% dig ANY a.ns.yp.to
...
;; ANSWER SECTION:
a.ns.yp.to.             259200  IN      A       131.193.36.25