a2.nic.sh has no MX records.
Question and response
Question
dig a2.nic.sh. MX
Answer
The response has no answer records.
Authority
nic.sh. 300 SOA a0.nic.sh. alerts.afilias.info. 4167604462 86400 7200 3600000 172800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0