usncsmtp.thruinc.com has no MX records.
Question and response
Question
dig usncsmtp.thruinc.com. MX
Answer
The response has no answer records.
Authority
thruinc.com. 14400 SOA a1.uberns.com. admin.thruinc.com. 2602170000 14400 7200 259200 14400
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0