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Use of the nsZones DNSBLs is free of charge for everybody. You can use nsZones public mirrors free by setting your mail server's DNSBL feature to query bl.nszones.com

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Professional DNSBL

Synchonize option is available for internet ISPs, organizations, networks, hosting providers, email providers.

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The bl.nszones.com Block List
The bl.nsZones.com is a realtime database of domain names, open-relay hosts, spammers hosts or dialup machines on the Internet.

As our primary mission, we want to promote a way to help the Internet users to prevent them from the hiddeous spammers activies.

All hosts in this list are periodically (every 6 months) re-checked and the secured hosts are automatically removed from our databases.

Black List Usage
Currently, the following zones exist:
  • bl.nszones.com combination of sbl.nszones.com and dyn.nszones.com in a single zone.
  • sbl.nszones.com (Open Relay, Hijacked PCs, Spam Source)
  • dyn.nszones.com (Dynamic, ADSL, Cable, no PTR Networks)
  • ubl.nszones.com (Domain Names, PTR of Dynamic Networks)

DNSBL queries are structured by the inverse IP address as a subdomain of the DNSBL zone. For example, to check that the general DNSBL test address of is listed in BL, query with any NS lookup tool such as...

You will receive an address 127.0.0.x - Open Relay, Hijacked PCs, Spam Source - Dynamic/ADSL/Cable Networks - Domain Names, PTR of Dynamic Networks

Attention: BL is checking only IPs and not Domain Names.
Do not use bl.nszones.com to check Domain Names.
For Domain Names check please use ubl.nszones.com

How to use nsZones Services
Doing a DNSBL lookup on a message at SMTP connect time is cheap in hardware cycles and system time. Your DNS server may even have it cached from the last time the spammer tried.

Mail rejected by a DNSBL during delivery is not silently discarded or lost. A DNSBL realtime rejection creates a delivery status notification to the sender identifying the cause of the rejection, thereby allowing troubleshooting on the sender's end.

By rejecting the connection attempt in real-time, a DNSBL also avoids any problems associated with an email system accepting delivery, closing the connection, and then trying to return the mail to a potentially forged address after the message is determined to be spam.

DNS is inherently very efficient, using minimal amounts of bandwidth. Using BL will use much less bandwidth than having to accept every spam and virus email sent to your email system. By rejecting these spam messages during the SMTP connection, no further data is sent thereby reducing overall bandwidth requirements. DNS caching by your local DNS server also prevents redundant queries from utilizing excessive bandwidth.

The use of the nsZones DNSBLs is free of charge for low-volume non-commercial use.

For professional use, internet ISPs, or hosting providers, we can provide your unlimited or dedicated realtime access to all nsZones DNSBLs from your network.

Free mirror service is provided to sites who are willing to host a public mirror (serving data to other free users).

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