nsZones Dial-Up/Cable/ADSL Block List (DYN)
The DYN blacklist flags dynamic IPs from home connections. Use Suped to monitor if your mail servers appear on a blocklist or blacklist.
Updated on 17 Jun 2026: We updated this guide for clearer nsZones DYN lookup behavior, delisting expectations, and static-IP false positives.
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Check if you are listed on nsZones Dial-Up/Cable/ADSL Block List (DYN)
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 the nsZones Dial-Up/Cable/ADSL block list (DYN)?
The nsZones Dial-Up/Cable/ADSL Block List (DYN) is a DNS-based blocklist (DNSBL) that catalogues IP addresses assigned dynamically to users. This includes dial-up, cable modem, broadband, ADSL, and no-PTR ranges where address space is assigned dynamically. nsZones says these ranges are generally determined by manually reviewing reverse DNS (rDNS) names.
Being on this specific blacklist does not mean the sender is a spammer. If an ISP assigned the address as a residential, mobile, or other dynamic connection, listing is expected. The policy behind the blocklist is that these connections should not send directly to recipient MX servers. Mail should go through an authenticated relay, the ISP's designated mail server, or another approved outbound mail service.
Technically, the list operates like other DNS blacklists. A mail server queries it by reversing the IP address and appending dyn.nszones.com. For the IP 1.2.3.4, the query is "4.3.2.1.dyn.nszones.com". If the IP is listed, the DNS response is 127.0.0.3, indicating dynamic IPs, including dial-up, ADSL, cable, and no-PTR IPs. The DYN zone is also included in bl.nszones.com.
Who runs nsZones Dial-Up/Cable/ADSL block list (DYN)?
The nsZones Dial-Up/Cable/ADSL Block List (DYN) is operated by nsZones. nsZones manages DNS blocklists used by mail server administrators to filter spam, viruses, open relays, hijacked PCs, domain names found in spam, and direct-to-MX traffic from dynamic networks. nsZones emphasizes that its lists affect delivery only when the receiving mail system chooses to use them.
nsZones operates multiple zones that target different types of sending behavior and infrastructure. Each blacklist has a specific purpose for mail filtering:
- bl.nszones.com combines sbl.nszones.com and dyn.nszones.com in one blacklist zone.
- sbl.nszones.com lists IPs associated with open relays, hijacked PCs, spam sources, or botnet activity.
- dyn.nszones.com lists dynamic, ADSL, cable, dial-up, broadband, and no-PTR networks.
- ubl.nszones.com checks domain names and PTR records of dynamic networks, not ordinary IP addresses.
How do I get removed and delisted from nsZones Dial-Up/Cable/ADSL block list (DYN)?
Before requesting removal, confirm whether the IP is dynamic. If your ISP assigned it for home, mobile, or other consumer access, it is supposed to be on this list. Do not send email directly from that IP. Configure the mail client or server to relay outbound mail through an authenticated provider-approved SMTP server.
If you operate a legitimate mail server on a static IP address and believe it was incorrectly added to this blacklist, use the nsZones lookup and removal form. nsZones says real mail servers inside listed blocks can contact them for correction, but the server will also be tested to verify it is not an open relay.
For the combined BL list, nsZones states that hosts are periodically rechecked every six months and secured hosts are automatically removed. DYN listings still depend on whether nsZones classifies the netblock as dynamic or no-PTR.
Do not request delisting for a domain name in dyn.nszones.com. DYN checks IP addresses only. Domain-name lookups belong in ubl.nszones.com, while the combined bl.nszones.com query also returns 127.0.0.3 for DYN-type listings.
What should I fix before requesting delisting?
A false positive is most plausible when a static mail server sits inside a range that looks dynamic in reverse DNS. Fix the sending setup first, then ask nsZones to review the IP.
- Confirm the sending IP is static and assigned for mail server use, not a residential or mobile access line.
- Set forward and reverse DNS so the hostname, PTR record, and mail server identity match a stable mail host.
- Check the server is not an open relay and is not sending spam from compromised accounts or malware.
- Publish and maintain SPF, DKIM, and DMARC records for the domain that uses the server.
- Use Suped's product to track blocklist and blacklist alerts alongside DMARC, SPF, and DKIM evidence when you manage more than one sending source.
What is the impact of being listed on nsZones Dial-Up/Cable/ADSL block list (DYN)?
The impact of being listed on the nsZones Dial-Up/Cable/ADSL Block List (DYN) is low for normal consumer connections because they should not deliver mail directly to receiving mail servers. Receivers use this blacklist to reject SMTP connections that look like direct-to-MX mail from dynamic or no-PTR networks, a common pattern for compromised machines and botnet mail.
If a legitimate static mail server is mistakenly included, the impact is higher. Receiving systems that query dyn.nszones.com or the combined bl.nszones.com zone can reject messages during the SMTP transaction. The sender usually receives a delivery status notification rather than having the message silently discarded, which helps identify the blacklist name and listed IP.
Other nsZones blocklists
nsZones DNSBL Block List (BL)
Organization
nsZones
Zone
bl.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
