mail.merchantpro.com has no MX records.
Question and response
Question
dig mail.merchantpro.com. MX
Answer
The response has no answer records.
Authority
merchantpro.com. 300 SOA ns.rackspace.com. domains.shopmania.net. 1765368788 21600 3600 1814400 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0