mailserver.local.okhosting.com has no CNAME records.
Question and response
Question
dig mailserver.local.okhosting.com. NS
Answer
The response has no answer records.
Authority
okhosting.com. 27 SOA okhosting.com. soporte\@okhosting.com.okhosting.com. 0 60 60 60 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0