subs.proxad.net has no MX records.
Question and response
Question
dig subs.proxad.net. MX
Answer
The response has no answer records.
Authority
subs.proxad.net. 86400 SOA ns2.proxad.net. hostmaster.proxad.net. 2024061901 21600 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0