mx.tixui.com has no CNAME records.
Question and response
Question
dig mx.tixui.com. NS
Answer
The response has no answer records.
Authority
tixui.com. 3305 SOA ns1.cloudcity.fi. hostmaster.cloudcity.fi. 2022012401 10800 15 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0