mailer.teo.lt has no CNAME records.
Question and response
Question
dig mailer.teo.lt. NS
Answer
The response has no answer records.
Authority
teo.lt. 959 SOA cash.ns.cloudflare.com. dns.cloudflare.com. 2396995902 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0