What are URI (link-based) blocklists?

URI blocklists track domain names appearing in message links. SURBL, URIBL, and similar lists identify domains associated with spam, phishing, or malware distribution. Filters check links in message content against these lists.

URI listing indicates the domain has appeared in spam campaigns, hosts phishing content, or distributes malware. This can affect legitimate senders who: use compromised link shorteners, include links to flagged services, or share domains with problematic content.

Impact differs from IP or sending domain blocklists. URI listings affect messages containing those links, regardless of sender reputation. Avoid linking to flagged domains, use your own domain for tracking links, and monitor URI blocklist status for any domains in your email content.