mail.webstep.net has no CNAME records.
Question and response
Question
dig mail.webstep.net. NS
Answer
The response has no answer records.
Authority
webstep.net. 23 SOA ns.webstep.cz. root.webstep.net. 2026022302 14400 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0