{"id":81441,"date":"2024-08-26T20:05:22","date_gmt":"2024-08-26T20:05:22","guid":{"rendered":"https:\/\/mailrelay.com\/glossary\/spamhaus\/"},"modified":"2026-10-19T12:16:47","modified_gmt":"2026-10-19T12:16:47","slug":"spamhaus","status":"publish","type":"glossary","link":"https:\/\/mailrelay.com\/en\/glossary\/spamhaus\/","title":{"rendered":"Spamhaus"},"content":{"rendered":"\n

Spamhaus<\/strong> is a non-profit organization that tracks spam and other internet threats and publishes blocklists<\/strong> of IP addresses and domains. Many mail servers check them before accepting an email: if the sender’s IP or domain appears on one of them, the message is rejected or goes to spam.<\/p>\n\n

It was founded by Steve Linford in London in 1998. Today it is headquartered in Andorra, and its lists protect millions of mailboxes around the world. That’s why appearing on a Spamhaus blacklist<\/a> is one of the most serious deliverability problems for anyone who sends emails.<\/p>\n\n

How do Spamhaus lists work?<\/h2>\n\n

When a server receives an email, it checks the originating IP against the Spamhaus lists with a DNS query that takes milliseconds. This is called a DNSBL (DNS-based blocklist).<\/p>\n\n

Spamhaus doesn’t block anything itself: it publishes the data. Each mail provider decides what to do with a listed sender, from rejecting it to sending it to the spam<\/a> folder.<\/p>\n\n

Spamhaus lists and what each one blocks<\/h2>\n\n
List<\/th>What it includes<\/th>Common reason<\/th><\/tr><\/thead>
SBL (Spamhaus Blocklist)<\/td>IP ranges of malicious networks<\/td>Sending spam or providing services to spammers<\/td><\/tr>
CSS (Combined Spam Sources)<\/td>IPs that send low-reputation email<\/td>Bulk sending without permission or with many complaints<\/td><\/tr>
XBL (Exploits Blocklist)<\/td>IPs of compromised machines<\/td>A virus or a bot sending spam without your knowledge<\/td><\/tr>
PBL (Policy Blocklist)<\/td>IPs that shouldn’t send email directly<\/td>Residential or dynamic IPs, defined by the provider itself<\/td><\/tr>
ZEN<\/td>SBL, CSS, XBL and PBL combined<\/td>It’s the list servers usually check<\/td><\/tr>
DBL (Domain Blocklist)<\/td>Low-reputation domains<\/td>Domains used in spam, phishing or malware<\/td><\/tr><\/tbody><\/table><\/figure>\n\n

The DBL isn’t part of ZEN because it blocks domains, not IPs. An email can run into problems because of the IP that sends it or the domains it contains.<\/p>\n\n

\"Infographic<\/figure>\n\n
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Send your campaigns from monitored IPs<\/strong><\/p>\n\n\n\n

Create your free Mailrelay account and send without setting up or maintaining your own mail server.<\/p>\n\n\n\n

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Create a free account<\/a><\/div>\n<\/div>\n<\/div><\/div>\n\n

How can you tell if you’re on a Spamhaus list?<\/h2>\n\n

The clearest signs are these:<\/p>\n\n