mail.clearcable.net has no MX records.
Question and response
Question
dig mail.clearcable.net. MX
Answer
The response has no answer records.
Authority
clearcable.net. 3600 SOA ns1.clearcable.ca. hostmaster.clearcable.ca. 1772695684 10800 3600 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0