mailserver.spireinns.co.uk has no CNAME records.
Question and response
Question
dig mailserver.spireinns.co.uk. NS
Answer
The response has no answer records.
Authority
spireinns.co.uk. 60 SOA ns1.spireinns.co.uk. postmaster.spireinns.co.uk. 2026022521 3600 600 604800 14400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0