smtp71.mediacombb.net has no MX records.
Question and response
Question
dig smtp71.mediacombb.net. MX
Answer
The response has no answer records.
Authority
mediacombb.net. 300 SOA pdns104.ultradns.com. internetsupport.mediacomcc.com. 2021063186 10800 3600 604800 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0