cart.sparklight.com has no MX records.
Question and response
Question
dig cart.sparklight.com. MX
Answer
The response has no answer records.
Authority
sparklight.com. 900 SOA ns1.cableone.net. dnsadmin.cableone.net. 293 10800 3600 2592000 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0