ns3.tucows.com has no MX records.
Question and response
Question
dig ns3.tucows.com. MX
Answer
The response has no answer records.
Authority
tucows.com. 60 SOA ns1.tucows.com. hostmaster.tucows.com. 1771760408 1200 3600 2419200 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0