108.205.88.in-addr.arpa has no MX records.
Question and response
Question
dig 108.205.88.in-addr.arpa. MX
Answer
The response has no answer records.
Authority
108.205.88.in-addr.arpa. 300 SOA neos.hkn.de. hostmaster.hkn.de. 1759405105 28800 7200 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0