mail.ithnet.com has no CNAME records.
Question and response
Question
dig mail.ithnet.com. NS
Answer
The response has no answer records.
Authority
ithnet.com. 3592 SOA ns.ithnet.com. hostmaster.ithnet.com. 2026020402 9000 1800 650000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0