I made a quick shell script to download the Spamhaus DROP list and create a block list for pf
https://gist.github.com/cypnk/a9831a099908a25a0cf35dcc2adaef16
The Spamhaus lists are really helpful if you're running a mail server
I'm using this on #OpenBSD. You can probably run this weekly via cron
Remember to reload pf after generating this list