mx.online.lv has no CNAME records.
Question and response
Question
dig mx.online.lv. NS
Answer
The response has no answer records.
Authority
online.lv. 10800 SOA ns.online.lv. hostmaster.online.lv. 2026011700 7200 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0