From: "Iñaki Baz Castillo" <ibc@...>
Date: 2009-02-23T20:01:56+09:00
Subject: Re: DNS MX lookup issue: local machine returned as MX for an 	non-existant domain!

2009/2/23 Yves-Eric <yemartin@gmail.com>:
> require 'resolv'
> domain = "i-dont-exist-iutjdfuyoxfugy.com"
> Resolv::DNS.open { |dns| dns.getresources(domain,
> Resolv::DNS::Resource::IN::MX)}
>
> On my development machine, this returns an empty list, as expected
> (the domain does not exist, it cannot have an MX record!).
> However, in my production environment, the same code returns:
> => [#<Resolv::DNS::Resource::IN::MX:0xb7cde342
> @exchange=#<Resolv::DNS::Name: mydomain.com.>, @preference=10>]
>
> It returns the production machine itself as a valid MX for a domain
> that does not exist!
>
> I double-checked on the command line that "nslookup -q=mx i-dont-exist-
> iutjdfuyoxfugy.com" indeed returns NXDOMAIN...
>
> Could someone please explain to me why this may be happening, and how
> to fix it? Howcome Resolv::DNS is returning an MX record for a domain
> that does not exist?! As a temporary workaround, I am simply filtering
> out mydomain.com from the MX list, but it really bugs me not knowing
> what the root of the problem is.

So you confirm that  "nslookup -q=mx i-dont-exist-iutjdfuyoxfugy.com"
also returns your local hostname?
If so, then it's not a bug in Ruby Resolv::DNS but in your DNS client
configuration in your server.


-- 
Iñaki Baz Castillo
<ibc@aliax.net>