Spam Blacklists
IP Blacklist Checker
Check an IP against 13 major RBLs — Spamhaus, SORBS, Barracuda, SpamCop and more.
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IP Blacklist Checker — Understanding RBLs
RBLs (Realtime Blackhole Lists), also called DNS blocklists (DNSBLs), are databases of IP addresses known to send spam or engage in abusive behaviour. Mail servers query these lists to decide whether to accept incoming email.
Spamhaus ZEN
The most widely used blacklist. ZEN is a combined list covering the Spamhaus Block List (SBL), Exploits Block List (XBL — compromised machines), and Policy Block List (PBL — IPs that should not send email directly). A listing here will block email to most major providers.
Barracuda Reputation Block List
Maintained by Barracuda Networks. Widely used by enterprise mail gateways. The self-service removal form at barracudacentral.org typically processes requests within 12 hours once the source of spam is fixed.
SORBS
The Spam and Open Relay Blocking System maintains several sub-lists covering spam sources, open relays, proxies, and dynamic IP ranges. Being on the SORBS dynamic list (duhl) is normal for residential IPs.
How to Get Delisted
Fix the underlying issue first (close open relays, patch malware, stop spam). Then visit each blacklist's website to submit a removal request. Spamhaus and Barracuda offer self-service. Others may require waiting for automatic expiry (typically 30–90 days).