spf.clipsan.net has no MX records.
Question and response
Question
dig spf.clipsan.net. MX
Answer
The response has no answer records.
Authority
clipsan.net. 900 SOA ns.web4u.cz. admin.web4u.cz. 2010070901 10800 3600 1209600 14400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0