ssoneweb004.telstra.com has no MX records.
Question and response
Question
dig ssoneweb004.telstra.com. MX
Answer
The response has no answer records.
Authority
telstra.com. 900 SOA adns05.bigpond.com. hostmaster.telstra.net. 2026022004 7200 1800 7200000 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0