mail5.pg7.mailxc.net has no CNAME records.
Question and response
Question
dig mail5.pg7.mailxc.net. NS
Answer
The response has no answer records.
Authority
mailxc.net. 1800 SOA kim.ns.cloudflare.com. dns.cloudflare.com. 2397972782 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0