dns4.shell.eu has no CNAME records.
Question and response
Question
dig dns4.shell.eu. NS
Answer
The response has no answer records.
Authority
shell.eu. 496 SOA dns1.shell.com. dns.shell.com. 3513 10800 1080 2419200 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0