ns3.corpinter.net has no MX records.
Question and response
Question
dig ns3.corpinter.net. MX
Answer
The response has no answer records.
Authority
corpinter.net. 600 SOA ns1.corpinter.net. dnsadmin.mercedes-benz.com. 2007074434 1800 900 604800 600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0