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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 dyn.nszones.com Block List

Dial-Up/Cable/ADSL IP Addresses
These are generally determined by manually looking at the reverse DNS names. If you have a real mail server in one of these blocks, please let us know so we can correct this list, but you will also be tested to verify you’re not an open relay. Note that this list contains Cable Modems, ADSL, Dial-Up and no PTR netblocks.

Being on this list does NOT mean you are a SPAMMER, it means you are connected to the net via ADSL/Cable/Dial-Up Modem, and your DNS shows this to be the case. You *should* be using your upstream ISP's mailserver.

dyn.nszones.com is a list of the world's dynamic IP addresses. Dial up connections, cable, broadband and ADSL customers. A list of netblocks where the address space is assigned dynamically to users and hosts regardless of the actual method of connecting those users and hosts to the network. Static IP addresses are NOT listed in DYN.

It is perfectly normal for dynamic IP addresses to be listed on the dyn.nszones.com. In fact all dynamic IP addresses are on the dyn.nszones.com. Dynamic connections could not have a mail server. The emails coming from this addresses are almost spam, hijacked PCs with worms or viruses.

Dynamic List Usage

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 DYN, query with any NS lookup tool such as...

You will receive an address: - Dynamic IPs (Dial up, ADSL, Cable, no PTR IPs)

dyn.nszones.com is included in bl.nszones.com

Attention: DYN is checking only IPs and not Domain Names.
Do not use dyn.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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