secure.emailsrvr.com has no MX records.
Question and response
Question
dig secure.emailsrvr.com. MX
Answer
The response has no answer records.
Authority
secure.emailsrvr.com. 300 SOA ns.rackspace.com. postmaster.emailsrvr.com. 1685284165 3600 300 1814400 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0