mx.abuse.tucows.com has no CNAME records.
Question and response
Question
dig mx.abuse.tucows.com. NS
Answer
The response has no answer records.
Authority
tucows.com. 60 SOA ns1.tucows.com. hostmaster.tucows.com. 1771908491 1200 3600 2419200 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0