dc-smtp.oxfordnetworks.com has no MX records.
Question and response
Question
dig dc-smtp.oxfordnetworks.com. MX
Answer
The response has no answer records.
Authority
oxfordnetworks.com. 3600 SOA dns1.firstlight.net. postmaster.no.email.please. 598392144 3600 600 2592000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0