mail.unbox.at has no MX records.
Question and response
Question
dig mail.unbox.at. MX
Answer
The response has no answer records.
Authority
unbox.at. 300 SOA ns1.cdom.de. webmaster.gfun.org. 2024091947 28800 7200 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0