mx.marconi-securesystems.com has no CNAME records.
Question and response
Question
dig mx.marconi-securesystems.com. NS
Answer
The response has no answer records.
Authority
marconi-securesystems.com. 3600 SOA dns.marconi-securesystems.com. hostmaster.marconi-securesystems.com. 1824497014 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0