spf.postal.brixly.uk has no MX records.
Question and response
Question
dig spf.postal.brixly.uk. MX
Answer
The response has no answer records.
Authority
brixly.uk. 1800 SOA justin.ns.cloudflare.com. dns.cloudflare.com. 2396962552 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0