_spfspam.uba.ar has no MX records.
Question and response
Question
dig _spfspam.uba.ar. MX
Answer
The response has no answer records.
Authority
uba.ar. 7200 SOA ns1.uba.ar. oper.ccc.uba.ar. 2025121100 600 1200 1296000 7200
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0