What is SURBL?

SURBL (Spam URI Realtime Blocklists) takes a different approach than traditional IP blocklists - it focuses on the links inside your emails rather than where the email came from. Even if your sending IP has a perfect reputation, including a link to a SURBL-listed domain will trigger spam filters.

Impact Level: High. SURBL is widely used by SpamAssassin, enterprise gateways, and many mailbox providers. A single bad link can torpedo an otherwise legitimate email.

What triggers listing:

• Domains appearing frequently in spam messages
• Phishing or malware distribution sites
• Affiliate links commonly used by spammers
• URL shorteners or redirectors used to mask spam destinations
• Newly registered domains used in spam (the "day-old bread" problem)

How to check: Query your domains at surbl.org/surbl-analysis

Delisting process: Submit a removal request at surbl.org/surbl-analysis (same page, scroll to removal section). You must demonstrate the domain is no longer associated with spam activity and has legitimate use. Response times vary; commercial SURBL services have faster review.

Before requesting removal:

• Ensure any compromised pages or scripts have been removed
• Check that your domain isn't being used in redirect chains by spammers
• Verify third-party services you integrate aren't adding spam links

Your IP reputation is like your ship's hull - but SURBL watches the cargo you're carrying. Load the wrong goods, and you'll be turned away regardless of how seaworthy your vessel appears.