https://www.spamhaus.org/blocklists/zen-blocklist/
ZEN Blocklist | Combined IP DNSBLs for effective email filtering
The Zen blocklist contains all IP-based DNSBLs offered free by Spamhaus (SBL, CSS, XBL, and PBL) to make querying simpler and faster.
zen blocklistemail filteringcombinedipeffective