mailx.itldc.com has no CNAME records.
Question and response
Question
dig mailx.itldc.com. NS
Answer
The response has no answer records.
Authority
itldc.com. 649 SOA anirban.ns.cloudflare.com. dns.cloudflare.com. 2396704591 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0