ns15.posti.fi has no MX records.
Question and response
Question
dig ns15.posti.fi. MX
Answer
The response has no answer records.
Authority
posti.fi. 300 SOA ns15.posti.fi. hostmaster.posti.com. 2015111471 10800 3600 2419200 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0