postcard.dih.oleane.net has no MX records.
Question and response
Question
dig postcard.dih.oleane.net. MX
Answer
The response has no answer records.
Authority
dih.oleane.net. 3600 SOA ns6.oleane.net. hostmaster.oleane.net. 2015020917 86400 3600 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0