>On a general point, is it possible to query a Name Server and determine if
>it will allow recursive queries (i.e. will act as your Local Name Server and
>do all your work for free)?
There's no way to tell with 100% accuracy. A lot of weird people set up
their DNS servers to lie if you aren't authorized to use it. For example,
one DNS server that I know of will return "Non-existent domain" if you look
up the MX record for yahoo.com (if properly set up, it should return a code
(5) that indicates that it won't allow you to use the DNS server).
Also, you really shouldn't use a DNS server for free unless you have been
given permission. If you do, you can't complain if a spammer hijacks your
mail server and tries sending millions of spams.
But, if you know what you are doing and feel it is appropriate (for
example, your ISP didn't give you a list of the DNS servers you can use),
you can run nslookup as follows:
nslookup
server 127.0.0.1 [replace 127.0.0.1 with the IP of
the server to check
set type=mx
yahoo.com
If you are allowed to use this DNS server, you should see a list of Yahoo
host names and IP addresses. If you see "non-existent domain", you're
dealing with one of those bozo servers. If you see an error message, or a
list of root servers (a.gtld-servers.net for example), then you can't use
the DNS server.
-Scott
---
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