mailrelay2c99.carrierzone.com has no MX records.
Question and response
Question
dig mailrelay2c99.carrierzone.com. MX
Answer
The response has no answer records.
Authority
carrierzone.com. 1200 SOA ns1.carrierzone.com. admin.carrierzone.com. 2017082759 86400 3600 3600000 345600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0