_spf1.imp.ch has no MX records.
Question and response
Question
dig _spf1.imp.ch. MX
Answer
The response has no answer records.
Authority
imp.ch. 3600 SOA ns1.imp.ch. noc.imp.ch. 2602200004 3600 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0