cust.asergo.com has no MX records.
Question and response
Question
dig cust.asergo.com. MX
Answer
The response has no answer records.
Authority
cust.asergo.com. 1800 SOA ns1.asergo.com. hostmaster.cust.asergo.com. 1685630305 10800 3600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0