mx.us-us-citruna.com has no MX records.
Question and response
Question
dig mx.us-us-citruna.com. MX
Answer
The response has no answer records.
Authority
us-us-citruna.com. 3600 SOA dns.us-us-citruna.com. hostmaster.us-us-citruna.com. 1126351975 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0