20.150.64.37.rev.sfr.net has no MX records.
Question and response
Question
dig 20.150.64.37.rev.sfr.net. MX
Answer
The response has no answer records.
Authority
rev.sfr.net. 86400 SOA nsrevprov.dns.sfr.net. support.dns.sfr.net. 2013072601 10800 3600 1814400 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0