nsZones DNSBL Block List (BL)
nsZones is a real-time IP blocklist and blacklist that identifies spam sources and open relays. It includes an option for express delisting from the service.
Updated on 17 Jun 2026: We updated this guide to clarify nsZones zone usage, IP-only BL checks, six-month rechecks, and practical delisting steps.
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Check if you are listed on nsZones DNSBL Block List (BL)
And 143 other blocklists.
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TechTheftSpamhaus0SpamCiscoNoSolicitadoURIBLabuse.roALPHANETAnonmailsAscamsBLOCKEDSERVERSCalivent NetworksEFnetJustSpamKempt.netNordSpamRV-SOFT TechnologyScientific SpamSpamikazeSpamRATSSPFBLSuomispamSystem 5 HostingTeam CymruValiditywww.blocklist.de Fail2Ban-Reporting ServiceZapBL2stepback.dkFayntic ServicesORB UKtechnoirc.orgTechTheftSpamhaus0SpamCiscoNoSolicitadoURIBLabuse.roALPHANETAnonmailsAscamsBLOCKEDSERVERSCalivent NetworksEFnetJustSpamKempt.netNordSpamRV-SOFT TechnologyScientific SpamSpamikazeSpamRATSSPFBLSuomispamSystem 5 HostingTeam CymruValiditywww.blocklist.de Fail2Ban-Reporting ServiceZapBL2stepback.dkFayntic ServicesORB UKtechnoirc.orgTechTheftSpamhaus0SpamCiscoNoSolicitadoURIBLabuse.roALPHANETAnonmailsAscamsBLOCKEDSERVERSCalivent NetworksEFnetJustSpamKempt.netNordSpamRV-SOFT TechnologyScientific SpamSpamikazeSpamRATSSPFBLSuomispamSystem 5 HostingTeam CymruValiditywww.blocklist.de Fail2Ban-Reporting ServiceZapBL2stepback.dkFayntic ServicesORB UKtechnoirc.orgTechTheftSpamhaus0SpamCiscoNoSolicitadoURIBLabuse.roALPHANETAnonmailsAscamsBLOCKEDSERVERSCalivent NetworksEFnetJustSpamKempt.netNordSpamRV-SOFT TechnologyScientific SpamSpamikazeSpamRATSSPFBLSuomispamSystem 5 HostingTeam CymruValiditywww.blocklist.de Fail2Ban-Reporting ServiceZapBL2stepback.dkFayntic ServicesORB UKtechnoirc.orgTechTheftWhat is nsZones DNSBL Block List (BL)?
The nsZones DNSBL Block List (BL) is a DNS blocklist (or blacklist) that maintains a real-time database of IP addresses associated with spam activity. This includes open relays, hosts known for sending spam, compromised PCs, and hosts on dynamic IP networks. Its primary goal is to give system administrators a DNS-based signal they can use to reduce unwanted spam.
The nsZones blacklist is structured into several zones for more granular filtering. The main zone, bl.nszones.com, combines sbl.nszones.com for open relays, hijacked PCs, and spam sources with dyn.nszones.com for dynamic, ADSL, cable, and no-PTR networks. The ubl.nszones.com zone covers domain names and PTR records associated with dynamic networks.
Technically, nsZones works like other DNS-based blacklists. A mail server can query the nsZones DNSBL by sending a DNS request with the reversed IP address of an incoming email connection. For example, to check the IP address 1.2.3.4, the server would query 4.3.2.1.bl.nszones.com. If the IP is listed, the blocklist returns a specific 127.0.0.x address indicating the reason for the listing:
- 127.0.0.2: The IP is listed for being an open relay, a hijacked PC, or a direct spam source.
- 127.0.0.3: The IP belongs to a dynamic, ADSL, or cable network, which is generally not supposed to send email directly.
- 127.0.0.4: The listing is related to domain names or PTR records of dynamic networks.
Do not use bl.nszones.com to check domain names. The BL zone checks IPs; use ubl.nszones.com for domain-name and PTR-related checks.
All hosts on this blocklist are re-checked every 6 months, and hosts that are no longer compromised or misconfigured are automatically removed over time.
Who runs nsZones DNSBL Block List (BL)?
The nsZones DNSBL Block List (BL) is operated by nsZones. nsZones positions the service as a defensive DNSBL that helps reduce spam volume for email systems. nsZones also states that blocklists do not actively block emails; they provide information that receiving mail servers can use to reject or filter messages according to their own policies.
nsZones describes public DNSBL use as free and also offers professional or dedicated real-time access for ISPs, hosting providers, email providers, and other higher-volume operators.
nsZones also runs a public mirror program, allowing volunteers to host copies of the nsZones databases on their own servers running Linux, Unix, or Windows. nsZones provides database access, software, and setup support, while the mirror operator manages the server.
How should mail teams use nsZones?
nsZones is designed to be queried at SMTP connect time. A receiving server checks the connecting IP before accepting the message, then rejects or filters the connection based on the receiving domain's local policy if the IP is listed.
- Use nsZones as one signal in a broader mail policy, not as the only reason to block mail. A listing can indicate an open relay, compromised host, dynamic IP, or missing reverse DNS.
- Query through a local DNS resolver where possible so repeated lookups can be cached and latency stays low.
- Check the exact zone and return code before changing outbound mail infrastructure, because a dynamic-IP listing needs different remediation than a compromised-host listing.
- Use Suped's DMARC reporting to confirm whether SPF, DKIM, and DMARC are passing for the domain while you investigate the listed IP. Suped will not remove an nsZones listing, but it helps separate authentication problems from IP reputation problems.
How do I get removed and delisted from nsZones DNSBL Block List (BL)?
Before requesting removal from any blocklist (blacklist), identify and resolve the underlying issue that caused the listing. This could involve securing a compromised machine, closing an open relay, stopping a spam-sending account, or moving outbound mail away from a dynamic residential connection.
Once the problem is fixed, you can request delisting. nsZones offers two paths for removal. You can check your IP status and request removal using their lookup and removal form.
The first option is automatic removal. nsZones says hosts are re-checked every 6 months, and secured hosts are removed automatically. Separately, listings can also expire free of charge after 60 months, or 5 years, after the last detected abuse from the IP address.
The second option is expedited manual express delisting. nsZones lists a 7.95 EUR fee for immediate removal and states that the same IP will not be listed again for the next 24 months.
What's the impact of being listed on nsZones DNSBL Block List (BL)?
The impact of being listed on the nsZones blacklist is usually low unless your recipients use mail systems that query nsZones. It is not known to be widely used by major mailbox providers like Gmail, Microsoft Outlook, or Yahoo, but smaller internet service providers, corporate mail servers, and hosting companies can still reference it.
If a recipient's mail server uses this blocklist, your email to that recipient can be rejected during the SMTP conversation or routed to the spam folder. A bounce message can mention nsZones, bl.nszones.com, or a 127.0.0.x return code, which helps confirm whether this specific blacklist caused the failure.
If delivery problems affect many unrelated recipients, investigate the listed IP, reverse DNS, recent sending behavior, and SPF, DKIM, and DMARC results before assuming nsZones is the only cause.
Other nsZones blocklists
nsZones Dial-Up/Cable/ADSL Block List (DYN)
Organization
nsZones
Zone
dyn.nszones.com
Type
IP
Impact
Low
Delisting
Manual
nsZones Spam Source Block List (SBL)
Organization
nsZones
Zone
sbl.nszones.com
Type
IP
Impact
Low
Delisting
Manual
nsZones SURBL/Spam URI Realtime Block List (UBL)
Organization
nsZones
Zone
ubl.nszones.com
Type
Domain
Impact
Low
Delisting
Manual
