mail.dfw-datacenter.com has no CNAME records.
Question and response
Question
dig mail.dfw-datacenter.com. NS
Answer
The response has no answer records.
Authority
dfw-datacenter.com. 1854 SOA ns.tailormadeservers.com. PostMaster.tailoredservers.com. 2009071700 28800 14400 360000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0