mail-a01.ithnet.com has no CNAME records.
Question and response
Question
dig mail-a01.ithnet.com. NS
Answer
The response has no answer records.
Authority
ithnet.com. 3583 SOA ns.ithnet.com. hostmaster.ithnet.com. 2026020402 9000 1800 650000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0