Leonardo from SPFBL shared the following information with me and I thought it would be useful to share it here with folks.
We created a new technology called SPFBL, that is like DNSBL (DNS Blackhole List) but the SPFBL (SPF Blackhole List) receive IP, sender and HELO as parameters at a TCP connection. The SPFBL is a GPL software (documentation is currently available only in Portuguese): https://github.com/leonamp/SPFBL
If the message is complained by users, these parameters gain negative points at a reputation system. A lot of Brazilian providers uses this technology and we receive all reputation data from them: http://spfbl.net/en/colaboradores/
To promote this new technology, we provide a DNSBL service based in SPFBL network reputation. Our DNSBL accept IPv4, IPv6 and domains.
The delist process can be done at this tool: https://matrix.spfbl.net/en/
If listed by bad reputation, the sender must use our feedback system, that runs at SMTP layer: http://spfbl.net/en/feedback