mail.ccrtc.com has no CNAME records.
Question and response
Question
dig mail.ccrtc.com. NS
Answer
The response has no answer records.
Authority
ccrtc.com. 59 SOA ns1.ccrtc.com. netadmin.ccrtc.com. 2026021300 14400 900 86400 240
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0