218.36.138.in-addr.arpa has no MX records.
Question and response
Question
dig 218.36.138.in-addr.arpa. MX
Answer
The response has no answer records.
Authority
218.36.138.in-addr.arpa. 3600 SOA edns116.ultradns.com. postmaster.218.36.138.in-addr.arpa. 2022012748 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0