What is the Spam Uniform Resource Identifier Real-time Block List (SURBL)?

The Spam Uniform Resource Identifier Real-time Block List (SURBL) is a collection of lists that identify Uniform Resource Identifier (URI) hosts, typically websites, that have appeared in unsolicited email messages. SURBL lists search incoming email message bodies for spam links to help evaluate whether the messages are unsolicited.  

For example, if is listed in the SURBL, then email messages with a message body containing this URI may be classified as unsolicited. URI Domain Name System Blacklists (DNSBLs) differ from other DNSBLs, which commonly list mail-sending IP addresses.

Key details

  • Type of list: SURBL is a public website blacklist. 
  • Listings occur: At the URI level. SURBL very rarely lists IP addresses as they are typically not used as a website address.
  • Criteria for getting listed: SURBL lists website URIs found in the body of a message associated with spam activity.  The URIs go to malicious sites or the URIs have received spam complaints that have turned the reputation negative. 
  • Impact on deliverability: High.
  • Regional impact: Global. This blacklist is used by many mailbox providers.
  • Getting removed from this blacklist:  To request removal, go to the SURBL Lookup page and follow the instructions on the removal form.


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