cust-136.179.17.0.switch.com has no MX records.
Question and response
Question
dig cust-136.179.17.0.switch.com. MX
Answer
The response has no answer records.
Authority
switch.com. 3600 SOA ns1.switch.com. hostmaster.switch.com. 2026022501 10800 900 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0