Schulte Blacklist: Email Blocklist Removal Guide
Independent DNSBL operated by a German researcher. Has been discontinued. DNS queries return NXDOMAIN or SERVFAIL. Historical reference only.
IP delisting
Konstant: Email Blocklist Removal Guide
Part of the MAPS (Mail Abuse Prevention System) relay blocklist family. MAPS was acquired by Trend Micro and the public free DNSBL service was discontinued. Enterprise subscription only.
Spamhaus ZEN: Email Blocklist Removal Guide
Composite zone combining SBL (spam sources), XBL (exploited IPs), and PBL (policy block list) into a single DNSBL query. The most widely deployed IP blocklist in the world. A listing…
