Spamhaus DNSBL Usage
There are two ways to query the Spamhaus DNSBLs (SBL, XBL, PBL and the combined ZEN lists), your mail server either sends queries out to Spamhaus's free public servers around the internet or sends queries locally to a private server on your own network. Which one you use, depends on your DNSBL needs and how you intend to use our DNSBLs. Free Use utilizes our free public servers, while Professional Use utilizes a data delivery system to synchronize DNSBL data with your servers.
Free Use
Spamhaus serves billions of DNSBL queries to the world every day, free of charge, from its over 40 public DNSBL servers spread across 18 countries. This free public DNSBL service is sustained thanks to donations of equipment and bandwidth by some of the internet's best organizations and networks (see Sponsors) and is backed financially by an autonomous commercial service that delivers Spamhaus data to ISPs, commercial networks and spam filter services. To qualify for free Spamhaus DNSBL query service, mail server operators need to ensure they meet the criteria for free use.
Use of the Spamhaus DNSBLs via DNS queries to our public DNSBL servers is free of charge if you meet all three of the following criteria:
1. Your use of the Spamhaus DNSBLs is non-commercial*, and
2. Your email traffic is less than 100,000 SMTP connections per day, and
3. Your DNSBL query volume is less than 300,000 queries per day.
If you do not fit all three of these criteria then please do not use our public DNSBL servers, instead see 'Professional Use' (below) which delivers our DNSBL data to your servers. If you are in any doubt as to whether you fit within our free use criteria, or think you may be likely to soon exceed our free use criteria, please switch to 'Professional Use'.
Spamhaus monitors use of its public DNSBL servers to identify installations exceeding the free use criteria in order to prevent a minority of heavy users from degrading the quality of the service to all other users of our free public DNSBL servers.
Caution: If your usage should exceed the free use criteria your access to Spamhaus's public DNSBL servers is very likely to be cut off without warning.
Professional Use
Use of the Spamhaus DNSBLs by ISPs, organizations and networks with email traffic higher than 100,000 SMTP connections per day or making over 300,000 DNSBL queries per day, or by commercial spam filter services, requires a subscription to the Spamhaus DNSBL Data Feed Service, a service designed for users with professional DNSBL query requirements.
Data Feed provides data synchronizations of the Spamhaus DNSBLs (SBL, XBL, PBL and also the DROP list) to a local DNS server on your network. Your mail servers therefore query a local DNS server on your network instead of going out to our public servers all over the world. This means DNSBL queries are super-fast, entirely under your control, and the service comes with a Service Agreement and Technical Support. For service pricing see the Data Feed service page. If unsure, simply try the Data Feed service first for 30 days free of charge before deciding or committing to it. There is a FAQ document for the service here.
http://www.spamhaus.org/organization/dnsblusage.html
