dns1-b.tor.radiant.net has no MX records.
Question and response
Question
dig dns1-b.tor.radiant.net. MX
Answer
The response has no answer records.
Authority
tor.radiant.net. 3600 SOA mrhmondr03-dnsaut-01.osc.tac.net. dnsadmin2.telus.com. 3 900 7200 3600000 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0