ns-a.blackspider.com has no MX records.
Question and response
Question
dig ns-a.blackspider.com. MX
Answer
The response has no answer records.
Authority
blackspider.com. 3600 SOA ns-a.blackspider.com. hostmaster.blackspider.com. 2025102100 3600 600 2419200 3600
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0