this will show if a dns server is resolving names
dig www.google.com @IP_of_dns_server
mx records:
To search for the MX records for the domain tech-recipes.com, use:
dig mx tech-recipes.com
This will query the DNS server configured in your operating system. Often times it is useful to query against a different DNS server. To perform the same query above against the name server ns3.notarealdomain.com:
dig @ns3.notarealdomain.com mx tech-recipes.com