dns3.shell.com has no CNAME records.
Question and response
Question
dig dns3.shell.com. NS
Answer
The response has no answer records.
Authority
shell.com. 564 SOA dns1.shell.com. dns.shell.com. 2830737 10800 1080 2419200 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0