What Is the Spamhaus
ZEN Blocklist?
ZEN consolidates several Spamhaus blocklists into one, making it a powerful tool for filtering email traffic.
What Is the Spamhaus
The Spamhaus ZEN Blocklist is a database maintained by the Spamhaus Project, an international non-profit organization dedicated to tracking spam operations and sources.
ZEN consolidates several Spamhaus blocklists into one, making it a powerful tool for filtering email traffic. It includes entries from the Spamhaus Block List (SBL), the Exploits Block List (XBL), and the Policy Block List (PBL). By using the ZEN Blocklist, email servers can effectively reduce the amount of spam received by identifying and blocking connections from IP addresses known to be problem sources. Many mail system administrators integrate ZEN into their email security measures to enhance filtering efficiency and protect users from unwanted or harmful messages.
ZEN Aggretes Multiple Blocklists Into One
ZEN unifies all of Spamhaus’ free IP-based DNSBLs into a single, powerful blocklist, enhancing both query speed and simplicity. This consolidated list includes the SBL, CSS, XBL, and PBL blocklists. For detailed policy descriptions of each component, refer to the individual pages linked below.
Rapid Querying
The ZEN dataset is an ultimate resource for efficient and rapid querying. In most setups, using ZEN eliminates the need to query other Spamhaus IP blocklists, reducing redundant queries and easing the load on your infrastructure.
Email administrators can use this DNSBL to significantly mitigate spam and malicious email threats, thereby enhancing security, reducing email infrastructure costs, and minimizing the need for additional human resources.
What’s Included in ZEN?
Each blocklist targets a specific type of behavior. Using a single blocklist independently limits the effectiveness of your data. However, leveraging ZEN as a comprehensive dataset ensures the best email protection available. The blocklists covered through ZEN are:
- Spamhaus Blocklist (SBL)
- Combined Spam Sources Blocklist (CSS)
- Exploits Blocklist (XBL)
- Policy Blocklist (PBL)
Due to its IP-centric nature, ZEN does not offer protection against malicious or suspicious domains. To achieve optimal catch rates, it’s recommended to use domain and hash blocklists in conjunction with ZEN once the email is accepted. Spamhaus provides the [Domain Blocklist (DBL)](https://www.spamhaus.org/blocklists/domain-blocklist/) for free. Learn more about why you should use domain and hash blocklists [here](https://www.spamhaus.com/resource-center/why-use-domain-and-hash-blocklists/).
How Zen Blocklist Technically Works
A DNS query to ZEN DNSBL often results in multiple distinct answers within a single DNS response packet, with one answer for each dataset where the IP is listed. Each dataset has a unique return code, so the information from ZEN is equivalent to separate queries to the SBL, CSS, XBL, and PBL DNSBLs, but with fewer resource demands.
You can leverage this data through SMTP server configurations for connection and SMTP transaction checks, as well as with open-source tools like SpamAssassin and Rspamd for content analysis. Plugins for both are readily available to minimize configuration time for users of Spamhaus Technology’s free Data Query Service.
Alternatively, you can seamlessly integrate ZEN with your existing anti-spam platforms. Technical support and integration information can be found here. The setup takes just minutes, providing you with instant, real-time protection.
The Spamhaus ZEN Dataset is Free to Use
Use of the Spamhaus DNSBLs is free of charge for low-volume, non-commercial users. If you’re unsure, please check our DNSBL usage criteria. Free accounts are made available through our partner, Spamhaus Technology – sign up to access the data via Data Query Service.
Tips for Keeping a Good IP Reputation
- Spamhaus’ data protects billions of mailboxes worldwide. To avoid getting listed and having your email service impacted, here are some key best practices:
- Restrict outbound SMTP traffic – Set up your firewall to allow outbound SMTP traffic (destination port 25) only if it comes from your mail server’s internal IP (if you have one).
- Infrastructure – Check your internet infrastructure providers, like ISPs. See reputation stats on ISPs/networks.
- Use double opt-in – This helps you avoid spam traps and ensures only real, interested recipients get your emails.
- Configuration – Make sure your hostname and HELO match, and that your reverse DNS (PTR record) points to the same hostname.
How to be removed from the ZEN Blocklist
If your IP is listed on the ZEN blocklist, you’ll also find a corresponding listing on one of these blocklists: SBL, CSS, XBL, or PBL. Go to https://check.spamhaus.org to use our IP and Domain Reputation Checker, where you can find more details and steps to fix the issue.