An RBL check queries an IP address against real-time blocklists (DNSBLs) to determine if it's flagged for spam, malware, or abuse. Use robtex.com to check any IP against major blocklists including Spamhaus, Barracuda, SORBS, and SpamCop instantly.
What Are RBLs?
Real-time blocklists (RBLs), also called DNSBLs, are databases of IP addresses associated with spam, malware, or other abuse. Mail servers query RBLs to decide whether to accept incoming connections.
If your IP appears on RBLs, your email may be rejected or filtered to spam - even if you're a legitimate sender.
How RBL Check Works
Enter an IP address to query it against multiple blocklists:
- Spamhaus - The most widely used blocklist, including SBL (spam), XBL (exploited hosts), and PBL (policy)
- Barracuda - Reputation list used by Barracuda appliances and others
- SORBS - Spam and Open Relay Blocking System
- SpamCop - User-reported spam sources
- UCEProtect - Multi-level listing from single IPs to entire ISPs
Results show listing status on each RBL, including listing reason when available.
Understanding Listing Reasons
Spam source - The IP sent spam directly or was reported by recipients.
Open relay/proxy - Misconfiguration allows unauthorized sending. Spammers exploit these.
Botnet/malware - The IP showed malicious behavior, possibly from compromised systems.
Dynamic/residential - Policy lists excluding IPs that shouldn't send email directly.
Poor reputation - Aggregate scoring based on multiple negative signals.
Why This Matters
Major email providers check multiple RBLs. Even one listing can devastate deliverability. Corporate mail servers often reject listed IPs outright.
Regular monitoring catches listings before they cause widespread delivery failures. Check your sending IPs proactively, not just when problems emerge.