ptr6.routit.net has no MX records.
Question and response
Question
dig ptr6.routit.net. MX
Answer
The response has no answer records.
Authority
routit.net. 900 SOA auth01-peer.ib.routit.net. noc.routit.nl. 287 1800 900 604800 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0