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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 ubl.nszones.com Block List

SURBLs, Spam URI Realtime Block Lists, are lists of Uniform Resource Identifier (URI) hosts, typically web site domains, that have been observed in unsolicited messages. SURBLs can be used to search incoming e-mail message bodies for similar sites to help evaluate whether the messages are unsolicited.

For example, if www.spamemailsever.com is blacklisted, then e-mail messages with a message body containing this URI may be classified as unsolicited.

SURBLs differ from prior DNSBLs, they check domain names and not IPs.

SURBL List Usage

For example, to check that the general UBL test address of spamemailsever.com is listed in UBL, query spamemailsever.com.ubl.nszones.com with any NS lookup tool such as...


If is listed you will receive an address

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