@jwildeboer I kind of retired from running mail servers. I mostly ran servers for orgs with between 50 and 200 users. False positives were always worse than false negatives. I tended to not block tlds or countries because some user always wanted mail from them.
I used postfix’s postscreen weighted RBLs feature to block spam. With a bit of tuning and the right selection of lists I managed to get rid of most spam. At some places I also ran spamassassin via mimedefang.