aus.zixmt1.zixworks.com has no MX records.
Question and response
Question
dig aus.zixmt1.zixworks.com. MX
Answer
The response has no answer records.
Authority
zixworks.com. 300 SOA ns.zixcorp.com. noc.zixcorp.com. 2026030401 86400 300 604800 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0