In the past I often got spammails from addresses like
Mitgliederservice <email@example.com> that slid through SpamAssassin. That mails differ from regular spam quite a lot.
- The mails are DKIM-Signed and pass the SPF check
- They are correctly formatted (ISO-8859-1)
- They are written in correct german
This tool takes a list of RIPE owner-handles and blocks all networks that are assigned to that owner. I don't expect any valuable traffic from that networks as all that ranges belong directly to a professional spammer.