mx2.caltech.iphmx.com has no NS records.
NS records for this zone are defined at iphmx.com.
NS records for this zone are defined at iphmx.com.
Question and response
Question
dig mx2.caltech.iphmx.com. NS
Answer
The response has no answer records.
Authority
iphmx.com. 3600 SOA ns1-93.akam.net. stbu-hostmaster\@cisco.com. 1771359044 3600 900 2419200 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0