ns1.ci.nttsvc.com has no MX records.
Question and response
Question
dig ns1.ci.nttsvc.com. MX
Answer
The response has no answer records.
Authority
ci.nttsvc.com. 600 SOA ns0.ci.nttsvc.com. hostmaster.ci.nttsvc.com. 1772015689 16384 1800 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0