mx.inbound.elasticemail.com has no CNAME records.
Question and response
Question
dig mx.inbound.elasticemail.com. NS
Answer
The response has no answer records.
Authority
elasticemail.com. 2686 SOA dns41.cloudns.net. support.cloudns.net. 2026021254 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0