117.203.in-addr.arpa has no MX records.
Question and response
Question
dig 117.203.in-addr.arpa. MX
Answer
The response has no answer records.
Authority
117.203.in-addr.arpa. 600 SOA pricus.starhub.net.sg. noc.starhub.net.sg. 2011053240 10800 3600 1209600 600
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0