require 'resolv'

dns = Resolv::DNS.new
domain = "oreilly.com"
dns.each_resource(domain, Resolv::DNS::Resource::IN::MX) do |mail_server|
    puts mail_server.exchange
end

dns.each_resource(domain, Resolv::DNS::Resource::IN::NS) do |nameserver|
    puts nameserver.name
end