smtp2.shopup.com has no MX records.
Question and response
Question
dig smtp2.shopup.com. MX
Answer
The response has no answer records.
Authority
shopup.com. 3600 SOA ns1. hostmaster. 20101290 900 600 86400 3600
Additional
. 0 OPT ; payload 4000, xrcode 0, version 0, flags 0