Operation timed out when digging mx

[Jonathan de Boyne Pollard]

T> Why would it time out for just the mx record on this server? 

Because the hostmaster of "caroldochenrealtors.com." has made a quite serious
error, and this just happens to be the way that your particular resolving
proxy DNS server software acts in the face of this particular error.  (Some
softwares flag a server failure.)

The delegation information published by the content DNS servers for a given
domain should be the same as, or a superset of, the delegation information
published by the content DNS servers for that domain's enclosing superdomain. 
(There's a quite serious bug in some resolving proxy DNS servers that can be
triggered if this is not the case.)  However, the hostmaster of
"caroldochenrealtors.com." has not followed this practice *at all*.

The delegation information for "caroldochenrealtors.com." that is published by
the "com." content DNS servers uses the intermediate domain names
"ns1.mintecommerce.com." and "ns2.mintecommerce.com.".  In contrast, the
delegation information for "caroldochenrealtors.com." that is published by the
"caroldochenrealtors.com." content DNS servers themselves uses the
intermediate domain names "64.105.113.115.caroldochenrealtors.com." and
"64.105.113.114.caroldochenrealtors.com.".

The irony is that the latter two domain names do not actually exist. 
Initially, the delegation information that is cached in one's resolving proxy
DNS server is the information published by the "com." content DNS servers,
with the intermediate names that do exist.  However: if, as a result of query
resolution causing one's resolving proxy DNS server to query the
"caroldochenrealtors.com." content DNS servers about something, the delegation
information is refreshed with that published by the "caroldochenrealtors.com."
content DNS servers themselves; all of a sudden the cached delegation
information uses non-existent intermediate names, and query resolution for
that domain name and all of its subdomains fails because there are no content
DNS servers to be found for it.

Next to this egregious error, the fact that the intermediate names
"64.105.113.115.caroldochenrealtors.com." and
"64.105.113.114.caroldochenrealtors.com." do not compress as well as the names
"ns1.mintecommerce.com." and "ns2.mintecommerce.com." would, seems paltry in
comparison.  (-: