ZapBL DNSBL
ZapBL is an IP-based blocklist (blacklist) featuring entries from private spam traps and direct mail reports.
Updated on 17 Jun 2026: We updated this guide to cover ZapBL's RHSBL and escalation rules.
Summarize with
Check if you are listed on ZapBL DNSBL
And 143 other blocklists.
Spamhaus
0Spam
Cisco
NoSolicitado
URIBL
abuse.ro
ALPHANET
Anonmails
Ascams
BLOCKEDSERVERS
Calivent Networks
EFnet
JustSpam
Kempt.net
NordSpam
RV-SOFT Technology
Scientific Spam
Spamikaze
SpamRATS
SPFBL
Suomispam
System 5 Hosting
Team Cymru
Validity
www.blocklist.de Fail2Ban-Reporting Service
ZapBL
2stepback.dk
Fayntic Services
ORB UK
technoirc.org
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 ZapBL DNSBL?
ZapBL DNSBL is a DNS-based blocklist (DNSBL) that lists IP addresses its administrators no longer wish to receive email from. According to its operators, it is a list of opinions, not a definitive declaration of a sender being a spammer. ZapBL itself does not block email. Any mail server administrator can query this blacklist to help filter incoming email, but usage is at their own discretion. The ZapBL project encourages those who use the list to inform them.
The listing policy is based on spam messages received at email addresses controlled by ZapBL administrators. These addresses can include personal accounts, dedicated spam traps, or catchall addresses. Listings are created manually by an admin or through an automated process that includes a manual review. Critically, ZapBL does not accept third-party reports or submissions for its blocklist.
- An IP address will be listed if it sends a spam message to a ZapBL admin email address.
- Servers sending non-delivery reports (NDRs) or virus rejection notices in response to spam with forged sender addresses can be listed as backscatter sources.
- Automated systems that reply to spam messages are also subject to being blocklisted.
- IPs that provide supplementary services, such as web hosting or DNS, to entities sending spam can also be added to the blacklist.
- Domains advertised in spam can be listed in ZapBL's RHSBL, although ZapBL says its admins try to avoid listing shared hosting domains.
Technically, the ZapBL DNSBL is IPv4-based. Mail servers query it using the zone dnsbl.zapbl.net. A query is performed by reversing the octets of an IP address and prepending it to the zone name. For example, the IP 192.168.1.2 would be queried as 2.1.168.192.dnsbl.zapbl.net. A positive result returns 127.0.0.2, which ZapBL lists as its only DNSBL response code.
ZapBL also operates a domain-based RHSBL at rhsbl.zapbl.net. A domain lookup uses the domain name before that zone, such as example.org.rhsbl.zapbl.net, and a positive result also returns 127.0.0.2.
Who runs ZapBL DNSBL?
The ZapBL DNSBL is maintained by a group known as the ZapBL admins. The project is based entirely on the mail they receive and their personal judgment of what constitutes unwanted email. To protect the integrity of the system and prevent targeted attacks, the administrators' email addresses and identities are kept confidential and are not disclosed.
How ZapBL escalations work
ZapBL can escalate listings when enough listed IPs appear inside the same network range. The stated threshold for a /24 is 3 listings. If more spam is received, the escalation can expand gradually up to the size of the IP allocation shown in WHOIS. ZapBL says supplementary service listings, such as IPs only providing web, MX, or DNS services to spammers, do not count toward that threshold.
For senders and providers, this means the fix should cover the full affected range, not only one listed host. Check for compromised accounts, misconfigured bounce handling, infected systems, and customers advertising spam domains before submitting a delisting request.
How do I get removed and delisted from ZapBL DNSBL?
Before requesting removal from this blocklist, identify and fix the root cause of the listing. This can involve securing a compromised server, removing a user account sending spam, or reconfiguring your mail server to stop sending backscatter. Once you have resolved the issue, use one of the following delisting paths.
- Most listings on the ZapBL blacklist are temporary and expire automatically after a certain period.
- The ZapBL website has a lookup tool. If a listing is eligible for public removal, a delisting option appears there.
- If a listing is permanent or cannot be publicly delisted, the official abuse contact registered for the IP address in its WHOIS record must submit the removal request. Requests should be made via their contact form.
ZapBL states that they will only communicate with the registered abuse contact for an IP block. End-users who find their IP on the blacklist should contact their Internet Service Provider for assistance. There is also a paid option for express delisting with a manual review, which can also be requested through the contact form.
What's the impact of being listed on ZapBL DNSBL?
The impact of being listed on the ZapBL DNSBL is usually limited. It is not one of the major blocklists used by large mailbox providers like Google or Microsoft. Its primary users are smaller organizations or independent mail server administrators who have chosen to incorporate this specific list into their anti-spam policies.
Even a listing on a low-impact blacklist can cause email delivery failures. If you send email to a recipient whose mail server uses ZapBL, your messages can be rejected, tagged, quarantined, or sent to the spam folder depending on that recipient's local policy. Investigate and request removal to protect deliverability.
