mail.mix-it.net has no MX records.
Question and response
Question
dig mail.mix-it.net. MX
Answer
The response has no answer records.
Authority
mix-it.net. 10800 SOA dns.mix-it.net. noc.mix-it.net. 2026020601 3600 900 1209600 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0