mx2.krystal.uk has no MX records.
Question and response
Question
dig mx2.krystal.uk. MX
Answer
The response has no answer records.
Authority
krystal.uk. 86400 SOA ns1.krystal.co.uk. admin.krystal.co.uk. 2026021901 3600 1800 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0