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Associated Documents

DNSBL Usage Terms
How Blocklists Work
Datafeed Service

ZEN is the combination of all Spamhaus IP-based DNSBLs into one single powerful and comprehensive blocklist to make querying faster and simpler. It contains the SBL, SBLCSS, XBL and PBL blocklists. should be the only DNSBL in your IP blocklist configuration. You should not use ZEN together with other Spamhaus IP blocklists, or with blocklists already included in our zones (such as the CBL) or you will simply be wasting DNS queries and slowing your mail queue. replaces in most configurations. If you are currently using you should replace with

Caution: Because ZEN includes the XBL and PBL lists, do not use ZEN on smarthosts or SMTP AUTH outbound servers for your own customers (or you risk blocking your own customers). Do not use ZEN in filters that do any ‘deep parsing’ of Received headers, or for anything other than checking IP addresses that hand off to your mailservers.

ZEN Return Codes

Querying returns the following result codes for listed entries (see the FAQs for a more complete return code table):

Return Codes Data Source Contains Direct UBE sources, spam operations & spam services Direct snowshoe spam sources detected via automation CBL (3rd party exploits such as proxies, trojans, etc.) End-user Non-MTA IP addresses set by ISP outbound mail policy

ZEN Usage

The ZEN blocklist can be used by all modern mail servers, by setting your mail server's anti-spam DNSBL feature (sometimes called "Blocklist Servers" or "RBL servers") to query:

Before including this blocklist as part of your mail server's spam filters please see Spamhaus's DNSBL Usage Terms to check if you qualify for free use.

DNSBL Usage Terms
Use of Spamhaus's free public DNSBL service is restricted to low-volume non-commercial users only. To make sure you qualify for free use, please see the terms:
DNSBL usage terms

The meaning of ZEN. We could have come up with a cool metaphorical explaination for using "ZEN", meaning a sense of organization, the combined focussed energy of our DNSBL teams... But really we chose the name because Zen was Spamhaus founder Steve Linford's German Shepherd. For many years Zen faithfully guarded the Spamhaus base in England, so we think it's apt that from the great kennel in the sky Zen lives on to help guard your networks and customers.
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