ns1.tierpoint.com has no MX records.
Question and response
Question
dig ns1.tierpoint.com. MX
Answer
The response has no answer records.
Authority
tierpoint.com. 300 SOA ns1.tierpoint.com. domains.tierpoint.com. 2017138520 10800 3600 2419200 300
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0