mail.dev.oktawave.com has no CNAME records.
Question and response
Question
dig mail.dev.oktawave.com. NS
Answer
The response has no answer records.
Authority
dev.oktawave.com. 4981 SOA ns1.oktawave.com. hostmaster.oktawave.com. 2024102207 28800 7200 345600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0