mx1.seofr.uk has no CNAME records.
Question and response
Question
dig mx1.seofr.uk. NS
Answer
The response has no answer records.
Authority
seofr.uk. 1800 SOA elma.ns.cloudflare.com. dns.cloudflare.com. 2397777668 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0