SURBL Checker
SURBL multi-list domain reputation lookup.
This is one independent signal used by the Domain Security Score, and can also be run on its own for any domain.
Based on: RFC 5782 — DNS Blacklists and Whitelists (DNSBL/RHSBL) · SURBL
About this validation
SURBL multi-list domain reputation lookup.
- Protocol / standard:
- Vendor documentation:
- Rules reviewed:
- Sep 6, 2026
SEOTechTests methodology: Data source: a live DNS query against SURBL's combined domain-reputation zone, following the RFC 5782 DNSBL mechanism. FAIL on a listing; PASS on NXDOMAIN; UNKNOWN on a query failure.
Standards and vendor-documented behavior can change. This reflects the source as last reviewed above, not a permanent guarantee.
FAQ
What does SURBL check for a domain?
SURBL maintains DNS-based lists of domains appearing in spam, phishing, or malware, built primarily from URLs seen in unwanted email and web content.
Why is SURBL a useful independent signal here?
SURBL's lists are compiled from different underlying data (spam/URL sightings) than Spamhaus's own feeds, so it can catch domains one source hasn't yet observed.
Does not being listed on SURBL mean the domain is clean?
No -- it means SURBL specifically hasn't listed it. Combine this with the other independent checks in this score rather than relying on any single list.
Why can this check return UNKNOWN?
A DNS query failure or a non-NXDOMAIN error (rather than a clean not-found) is reported as UNKNOWN, never as a false PASS.