gerwestsmtp.thruinc.com has no CNAME records.
Question and response
Question
dig gerwestsmtp.thruinc.com. NS
Answer
The response has no answer records.
Authority
thruinc.com. 5674 SOA a1.uberns.com. admin.thruinc.com. 2602260001 14400 7200 259200 14400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0