return codes are explained
http://rfc-clueless.org/
usage policy is not so clear but the FAQ implies that it’s just free to use for everyone
+ many timeouts
+ first noticed in 2014 and deactivated
+ retried in 2023 and still the case
http://spameatingmonkey.com/
lists IPs
that sent backscatter
no news on http://apews-user.blogspot.com/ since 2014
not further looked into because of the above
https://www.dnswl.org/
+ seems to be run with best intentions but has had issues from what I have heard from some users
+ IRC channel has some activity
+ usage policy relatively clear
+ free within certain limits
+ listing policy
+ self-service
+ return codes are documented
00_E_FOCUS
http://stopspam.org/rblcheck/index.php
different kinds of lists