Free Blocklist Checker

Check your IP or domain against 50+ major email blocklists including Spamhaus, SURBL, and Barracuda.

Blocklist Reputation Check

Check your IP address or domain across 50+ email blocklists including Spamhaus, SURBL, and Barracuda

Enter an IP address (for DNSBL) or domain (for URIBL)

Understanding Blocklists

Email blocklists (also called DNSBLs/RBLs for IPs and URIBLs for domains) are databases of IP addresses and domains known for sending spam. Being listed can severely impact your email deliverability.

Severity Levels

criticalMajor impact on deliverability. Used by most email providers. Immediate action required.
highSignificant impact. Used by many providers. Should be addressed promptly.
mediumModerate impact. Monitor and delist when possible.
lowLimited impact. Low priority for delisting.

What is an Email Blocklist?

Overview

Email blocklists (also called blacklists, DNSBLs, or RBLs) are real-time databases that track IP addresses and domains associated with spam, malware, or other email abuse. Email providers query these lists during message delivery to filter incoming mail. Being listed can severely impact deliverability, causing emails to be rejected or sent to spam folders.

Comprehensive Monitoring

Our blocklist checker monitors your IP addresses and domains against 50+ major email blocklists used by ISPs and spam filters worldwide. Being listed on just one critical blocklist can block 80% or more of your emails from reaching inboxes.

Critical Blocklists Checked

  • Spamhaus (SBL, XBL, PBL, DBL, ZEN): Most widely used blocklist, trusted by major ISPs
  • SURBL Multi: Domain/URL reputation for content links
  • URIBL (Black, Grey, Red): URI-based spam detection
  • Barracuda Reputation: Used by Barracuda spam filters globally
  • SpamCop: Community-driven spam reporting network
  • Invaluement: Real-time spam trap monitoring

How Email Blocklists Work

Blocklists track IP addresses and domains associated with spam. Email providers query these lists during message delivery:

  1. Incoming email arrives from IP address 192.0.2.1
  2. Mail server checks if 1.2.0.192.zen.spamhaus.org resolves (reversed IP + blocklist zone)
  3. If it resolves, the IP is listed → email rejected or marked as spam
  4. If NXDOMAIN (not found), the IP is clean → email proceeds

Types of Blocklists

DNSBL (DNS Blocklist) - For IP Addresses

Checks the reputation of your email sending servers. Common reasons for listing:

  • Spam complaints from recipients
  • Compromised servers sending bulk spam
  • Poor list hygiene (high bounce rates)
  • Spam trap hits
  • Residential/dynamic IP ranges

URIBL (URI Blocklist) - For Domains

Checks domains and URLs included in your email content. Listed if:

  • Domain appears in spam campaigns
  • Associated with phishing or malware
  • Newly registered domain (sometimes flagged)
  • Domain reputation issues

Best Practices

  • Implement SPF, DKIM, and DMARC authentication
  • Use double opt-in for email lists
  • Process unsubscribes promptly
  • Monitor spam complaint rates (<0.1% target)
  • Maintain clean email lists (remove hard bounces)
  • Avoid shared hosting with poor IP reputation
  • Set up feedback loops with major ISPs
  • Monitor regularly with our blocklist checker