IP Reputation Check - Complete Blocklist Analysis

An IP reputation check queries an IP address against DNS blocklists (DNSBLs) and threat intelligence databases to determine if it's associated with spam, malware, or abuse. Use robtex.com to check any IP against 100+ blocklists and threat feeds in real-time.

What We Check

Our IP reputation scanner combines multiple data sources simultaneously:

Threat Intelligence Databases

  • IPsum - Crowdsourced threat intelligence with reputation scores (0-10 scale)
  • FireHOL - Aggregated blocklists from 85+ security research feeds
  • Maltrail - Known malware, C2 infrastructure, and suspicious hosts

Network Threat Detection

  • Tor Exit/Relay Nodes - Detection of Tor network infrastructure
  • C2 Servers - Known botnet command-and-control infrastructure

DNS Blocklists (RBLs) - Over 100 real-time blocklists including Spamhaus ZEN, Barracuda, SpamCop, SORBS, UCEPROTECT, and many more. These are the lists that email servers query to decide whether to accept mail.

Understanding Results

Database Sources stream in first (IPsum, FireHOL, Tor, C2, Maltrail):

  • 🔴 Listed - IP appears in this threat database with details
  • 🟢 Clean - IP is not in this database

DNS Blocklists query in parallel:

  • 🔴 Listed - IP appears on this RBL (often with a reason code)
  • 🟢 Clean - IP is not currently listed
  • ❌ Error - The blocklist didn't respond (temporary, not concerning)

Results stream in as each source responds - typically completing within seconds.

Why IP Reputation Matters

Email Deliverability - Being listed on Spamhaus, Barracuda, or SpamCop can cause emails to be rejected or filtered to spam. Even one major listing can devastate delivery rates.

Security Posture - IPs appearing on threat intelligence feeds like IPsum or FireHOL may indicate compromise, malware infection, or association with malicious activity.

Business Reputation - Shared hosting, cloud IPs, or acquired addresses may carry previous owners' poor reputation.

Key Sources Explained

Threat Intelligence

IPsum Score - Crowdsourced reputation scoring from 0-10. Higher scores indicate more reported malicious activity. Score 3+ warrants investigation.

FireHOL - Aggregates data from 85+ blocklists including abuse.ch, AlienVault, Blocklist.de, BruteForce, Emerging Threats, and more. Shows which specific lists flagged the IP.

Maltrail - Maintained by security researchers, tracks known malware, ransomware C2, and suspicious infrastructure.

DNS Blocklists

Spamhaus ZEN - The most widely used blocklist, combining SBL (spam sources), XBL (exploited hosts), and PBL (policy-based exclusions for dynamic IPs).

Barracuda - Popular with enterprise email systems. Aggressive listing but responsive delisting.

SpamCop - User-reported spam with automatic expiration. High turnover.

SORBS - Multiple specialized lists for spam, proxies, and dynamic IPs.

UCEPROTECT - Three levels: L1 (single IP), L2 (IP range), L3 (entire ASN). Controversial escalation policy.

Common Listing Reasons

Spam source - Direct spam sending or user reports

Open relay/proxy - Misconfigured server allowing unauthorized sending

Botnet/malware - Compromised system participating in attacks

Tor exit node - IP used as Tor exit relay (not malicious, but filtered by some)

Dynamic/residential - Policy-based listing for IPs that shouldn't send email directly

Poor sender reputation - Aggregate scoring from multiple negative signals

→ Check an IP address on robtex.com

FAQ

My IP is listed - will my email be blocked?
Depends on which lists and recipients' filtering. Spamhaus listings cause widespread blocks. Minor lists have less impact. Some recipients reject; others just increase spam scoring.
How do I get delisted?
Each blocklist has its own removal process. First fix the underlying problem (compromised account, infected server, etc.) or you'll be relisted immediately. Most major RBLs have self-service removal.
Why am I listed when I don't send spam?
Common causes: compromised email accounts, malware on your network, shared hosting with spammers, inherited IP reputation, or being on dynamic IP space (policy listings).
What's the difference between DNS RBLs and threat intelligence databases?
DNS RBLs are queried in real-time by email servers during delivery. Threat databases like IPsum and FireHOL aggregate data from multiple sources for security research and blocking. Both indicate problems, but RBL listings directly impact email delivery.
How often should I check my sending IPs?
Weekly for production mail servers. Immediately when you notice deliverability drops. Consider automated monitoring for critical infrastructure.
What's the difference between IP and domain reputation?
IP reputation reflects the sending server's history. Domain reputation reflects the domain's history across all sending IPs. Both affect deliverability. Check domain reputation on robtex.com →