df.spf.jisc.ac.uk has no MX records.
Question and response
Question
dig df.spf.jisc.ac.uk. MX
Answer
The response has no answer records.
Authority
jisc.ac.uk. 3600 SOA ns11.ja.net. hostmaster.ns11.ja.net. 2014073547 43200 3600 3600000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0