mx.stone25.com has no NS records.
NS records for this zone are defined at stone25.com.
NS records for this zone are defined at stone25.com.
Question and response
Question
dig mx.stone25.com. NS
Answer
The response has no answer records.
Authority
stone25.com. 3600 SOA dns.stone25.com. hostmaster.stone25.com. 1359279846 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0