Spamhaus provides a free reputation checker that lets you verify if an IP address or domain is listed on their blocklists. It’s a trusted resource for diagnosing email delivery issues and identifying malicious activity.

🔍 Check IP addresses and domain names against Spamhaus blocklists

📧 Diagnose email delivery problems caused by poor sender reputation

🛡️ Identify malicious domains, compromised servers, or spam sources

⚡ Fast, reliable, and widely used by ISPs and mail providers

🌐 Web‑based tool, no installation required

🤝 Maintained by the Spamhaus Project, a global authority on spam and cyber threats

Perfect for: Sysadmins, email service providers, and security‑conscious users who need to verify sender reputation.