mail.dev.uk2.net has no CNAME records.
Question and response
Question
dig mail.dev.uk2.net. NS
Answer
The response has no answer records.
Authority
dev.uk2.net. 6697 SOA ns1.uk2.net. hostmaster.uk2.net. 2025111905 86400 1800 604800 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0