smtp.standard24.net has no CNAME records.
Question and response
Question
dig smtp.standard24.net. NS
Answer
The response has no answer records.
Authority
standard24.net. 300 SOA x.ns.joker.com. hostmaster.joker.com. 2025111452 14400 3600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0