78.4.in-addr.arpa has no MX records.
Question and response
Question
dig 78.4.in-addr.arpa. MX
Answer
The response has no answer records.
Authority
78.4.in-addr.arpa. 3600 SOA ns2.Level3.net. dns.level3.net. 2026030401 7200 600 2592000 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0