mail.skillgate.com has no CNAME records.
Question and response
Question
dig mail.skillgate.com. NS
Answer
The response has no answer records.
Authority
skillgate.com. 3515 SOA ns1.kloudns.co.uk. dns-admin.katapult.io. 1770632435 28800 7200 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0