dns.21gambling.com has no MX records.
Question and response
Question
dig dns.21gambling.com. MX
Answer
The response has no answer records.
Authority
21gambling.com. 3600 SOA dns.21gambling.com. hostmaster.21gambling.com. 1790883370 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0