Complete blocklist directory: All major IP and domain blocklists with lookup and delisting URLs
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High-impact IP blocklists
- Spamhaus ZEN: composite zone covering SBL (spammer IPs), XBL (exploited machines), and PBL (IPs not authorized to send email). The most widely queried blocklist in email filtering worldwide.
- Barracuda BRBL: heavily used by corporate mail gateways. Can block delivery to mid-market companies even when major ISPs show clean.
Other IP blocklists
- SpamCop: complaint-based. Listings expire automatically when spam reports stop. Aggressive but short-lived.
- SORBS (Software of Internet Abuse Research System): covers dynamic IPs, open relays, and known spam sources. Patchy enforcement across receivers.
- UCEPROTECT: three tiers, from single-IP to full ASN blocks. Controversial auto-listing practices. Paid delisting required for higher tiers.
Domain and URI blocklists (flag your From domain or links in your email body)
- Spamhaus DBL: flags your sending domain or URL domains in message body. A clean IP won't protect you if your domain is listed here.
- SURBL (Spam URI Realtime Blocklists): checks links embedded in email body, not sender IP. An entirely separate reputation surface.
- Cloudmark (now Proofpoint): used by large ISPs including Comcast and Cox. No public lookup. Contact Cloudmark directly for listing information.
Commercial and internal systems (no public lookup)
- Proofpoint: used by enterprise mail gateways. Listing data isn't publicly available.
- Microsoft SmartScreen: internal to Outlook and Hotmail. Influenced by your sender reputation and complaint rates.
- Google Postmaster Tools: not a blocklist, but domain reputation here directly affects Gmail delivery. Free to set up and worth monitoring.
Defunct blocklists (remove from automated checks, they return false positives now)
- MAPS (merged into Trend Micro's system)
- CBL (merged into Spamhaus XBL)
- NJABL (shut down)
- AHBL (shut down, returns false positives for all queries now)
Multi-list checkers (scan dozens of lists at once)
- MXToolbox: 100+ lists, free monitoring with email alerts
- MultiRBL: 300+ lists. Includes defunct ones, so read results carefully before acting.
- DNSBL.info: 36 active lists, clean interface
If you want to run a quick scan right now, our free blocklist checker covers the highest-impact lists in one shot. For the removal process once you're listed, the delisting guide walks through each major blocklist's process.
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