a.nic.casa has no MX records.
Question and response
Question
dig a.nic.casa. MX
Answer
The response has no answer records.
Authority
nic.casa. 900 SOA a.nic.casa. admin.tldns.godaddy. 1772026975 1800 300 604800 1800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0