uksmtp.thruinc.com has no CNAME records.
Question and response
Question
dig uksmtp.thruinc.com. NS
Answer
The response has no answer records.
Authority
thruinc.com. 3692 SOA a1.uberns.com. admin.thruinc.com. 2602260001 14400 7200 259200 14400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0