mail.lena-k.com has no CNAME records.
Question and response
Question
dig mail.lena-k.com. NS
Answer
The response has no answer records.
Authority
lena-k.com. 2560 SOA ns1.loopiagroup.com. dnsadmin.loopiagroup.com. 1770783340 7200 2048 1048576 2560
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0