spf.yettel.rs has no CNAME records.
Question and response
Question
dig spf.yettel.rs. NS
Answer
The response has no answer records.
Authority
yettel.rs. 3600 SOA dinosaur.cetin.rs. Administrator. 259 600 300 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0