delta.securenet-server.net has no MX records.
Question and response
Question
dig delta.securenet-server.net. MX
Answer
The response has no answer records.
Authority
securenet-server.net. 3587 SOA ns1.wolverinedns.com. monitor.ace-host.net. 2026021901 7200 7200 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0