https://www.spamhaus.org/organization/dnsblusage/
listing policies are clearly documented
return codes are clearly documented
+ history of grandeur and retaliation listings
+ https://www.heise.de/hintergrund/Spam-Golem-291396.html
http://www.surbl.org/
good reputation
lists domains/URIs
usage policy not quite clear ATM
return codes documented: binary
http://mailspike.net/usage.html
- reputation-based
- http://www.isipp.com/email-accreditation/iadb-query-instruction/
- requires signup
- not quite a usage policy, but seems ok
- strange split of ipv4 and ipv6
- seems dead?
+ lists IPs
+ response codes according to their reputation, both positive and negative
+ listing policy documented
+ usage policy documented
+ https://www.isipp.com/for-isps/iadb-query/
+ usage policy seems clear: It is free to query all of the IADB, IADB2, and WADB.
+ not quite a whitelist but closer to whitelist than blacklist
+ listing policy seems to be: get certified by them (for a fee) https://www.isipp.com/email-accreditation/faq/#pricing
+ response codes are documented