_internal.virginmedia.co.uk has no MX records.
Question and response
Question
dig _internal.virginmedia.co.uk. MX
Answer
The response has no answer records.
Authority
virginmedia.co.uk. 1800 SOA ns1.virginmedia.net. hostmaster.virginmedia.net. 2025082842 86400 7200 1209600 1800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0