ns4.mixarthost.com has no MX records.
Question and response
Question
dig ns4.mixarthost.com. MX
Answer
The response has no answer records.
Authority
mixarthost.com. 86400 SOA ns3.mixarthost.com. info.dominet.net. 2026022701 3600 7200 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0