Email blocklist · DNSBL · URLs / domains
TUE · 28 JUL 2026
SURBL
About
The dominant URL-based blocklist. Matches against domains and URLs in message body, not IPs in headers. Complementary to Spamhaus DBL.
Listing criteria
URL blocklist that matches against domain names found inside message bodies. Several sub-lists for phishing, malware, abuse and spam. Useful as a complement to IP-based filtering.
How to query
For an IP address 1.2.3.4, query reversed-octets-dot-zone:
dig +short 4.3.2.1.multi.surbl.orgA returned IP (such as 127.0.0.2) means listed. Each blocklist has its own set of return codes meaning different things; the operator's documentation explains theirs.