Email Blacklists (DNSBL/RBL) - Complete Guide

There are thousands of blocklists managed by various organizations, each with different specifications for how a domain or IP ends up on their list. Sometimes known as a DNSBL (Domain Name System Blacklist) or RBL (Realtime Blackhole List), these services are spam blocking lists used by ISPs and mailbox providers to filter unwanted email.

Some lists have a more significant impact on email delivery than others. Understanding which blacklists matter most for your email deliverability is crucial for maintaining good sender reputation.

Understanding Blacklist Impact

High Impact Blocklists

These are the most critical lists that can cause significant delivery problems:

• Spamhaus is the most well-respected and widely used blocklist in the world. A listing at Spamhaus will have a negative effect on your ability to deliver emails and can cause bounce rates of over 50%. Evidence suggests that most of the top North American ISPs use Spamhaus to inform blocking decisions.

• Barracuda is widely used by enterprise email security appliances and can significantly impact B2B email delivery.

• SpamCop can have a significant impact on B2B email campaigns, though it is not as widely used by major North American ISPs.

Medium Impact Blocklists

These lists can impact delivery but are less widely used:

• SORBS uses several methods to identify potential spammers. Most of their lists use spam traps to identify problematic senders. SORBS will also list a sender based on user complaints or if administrators have received spam from the sender.

• UCEPROTECT maintains multiple levels of blacklists, with Level 1 being the most commonly used.

• Abusix provides commercial blacklist services that are used by many European ISPs and enterprises.

Low Impact Blocklists

These lists are unlikely to significantly impact delivery but may be used by smaller providers:

• Many of these are regional or specialized lists that focus on specific types of abuse or geographic areas.
• Some are community-maintained lists that may not have the same level of accuracy as major commercial lists.

How Email Blacklists Work

Email blacklists operate by maintaining databases of IP addresses or domains that have been identified as sources of spam, malware, or other abusive email activity. When an email server receives a message, it can query these blacklists to determine if the sending IP or domain is listed.

Types of Blacklists

IP-based Blacklists (DNSBL) - Check the IP address of the sending mail server - Most commonly used by major ISPs and email providers - Examples: Spamhaus ZEN, Barracuda, SpamCop

Domain-based Blacklists (RHSBL) - Check the domain name in email headers or content - Used to identify spam domains and phishing sites - Examples: Spamhaus DBL, SURBL, URIBL

Specialty Blacklists - Focus on specific types of abuse (TOR nodes, open proxies, etc.) - Used by security-conscious organizations - Examples: DroneBL, Backscatterer, CYMRU Bogons

How to Check Your Blacklist Status

You can check if your IP address or domain is listed on any of these blacklists using our Spam Database Lookup Tool. This tool will check your IP or domain against all the major blacklists and provide detailed information about any listings found.

What to Look For

When checking your blacklist status, pay attention to:

1. High-impact listings - These require immediate attention
2. Listing reasons - Understanding why you were listed helps prevent future issues
3. Delisting procedures - Each blacklist has different removal processes
4. Prevention strategies - Learn from listings to improve your email practices

Getting Delisted from Blacklists

If you find yourself listed on a blacklist, follow these steps:

1. Identify the Listing Reason

Most blacklists provide information about why an IP or domain was listed. Common reasons include: - Sending spam or unsolicited bulk email - Operating an open relay or proxy - Being infected with malware - Poor email authentication setup - High bounce rates or complaints

2. Fix the Underlying Issue

Address the root cause before requesting delisting: - Implement proper email authentication (SPF, DKIM, DMARC) - Clean your email lists and remove invalid addresses - Secure your email infrastructure - Review and improve your email sending practices

3. Contact the Blacklist Operator

Follow their specific delisting procedures: - Most blacklists have online delisting forms - Provide evidence that the issue has been resolved - Be patient - delisting can take 24-48 hours

4. Monitor and Prevent Future Listings

• Regularly check your blacklist status
• Monitor your email metrics (bounces, complaints, engagement)
• Maintain good sending practices

For more detailed information about getting off email blacklists, see our comprehensive guide: How to Get Off of Email Blacklists

Complete Blacklist Reference

Below is a comprehensive list of all the blacklists we monitor, organized by impact level. Each entry includes the lookup zone and a direct link to check your status.

High Impact Blocklists

Major IP Blacklists

Spamhaus ZEN - Combined IP blacklist (SBL, XBL, PBL) for spam, botnets, infected IPs - Lookup Zone: zen.spamhaus.org - Check Now

Barracuda - IP reputation blacklist by Barracuda Networks - Lookup Zone: b.barracudacentral.org - Check Now

SpamCop - Blacklist of IPs sending to spam traps or reported as spammers - Lookup Zone: bl.spamcop.net - Check Now

Abusix Mail Intelligence (IP) - Trap-based IP blacklist for spam, exploits, botnets - Lookup Zone: ip.mail.abusix.zone - Check Now

UCEPROTECT L1 - Abusive IPs detected by UCEPROTECT - Lookup Zone: dnsbl-1.uceprotect.net - Check Now

0SPAM - Free DNSBL for IPs sending spam to spam traps - Lookup Zone: 0spam.fusionzero.com - Check Now

0SPAM RBL - 0SPAM's real-time DNSBL for IPs detected sending spam - Lookup Zone: rbl.0spam.org - Check Now

SWINOG - Swiss Network Operators Group DNSBL for spam and abuse - Lookup Zone: dnsbl.swinog.ch - Check Now

TRIUMF - TRIUMF DNSBL for spam and open relay detection - Lookup Zone: dnsbl.triumf.ca - Check Now

NoSolicitado - Spanish-language DNSBL for spam and abuse sources - Lookup Zone: bl.nosolicitado.org - Check Now

Abusix Exploit - Abusix DNSBL for IPs involved in exploits, malware, and abuse - Lookup Zone: exploit.mail.abusix.zone - Check Now

Major Domain/URI Blacklists

Spamhaus DBL - DNSBL for domains seen in spam, phishing, and malware - Lookup Zone: dbl.spamhaus.org - Check Now

SURBL multi - Aggregated DNSBL for domains/URLs found in spam messages - Lookup Zone: multi.surbl.org - Check Now

URIBL - Blacklist for domains appearing in unsolicited or bulk email - Lookup Zone: multi.uribl.com - Check Now

ivmURI - Invaluement's DNSBL for domains and URIs found in spam and phishing emails - Lookup Zone: dnsbl.ivmURI.com - Check Now

Abusix Mail Intelligence Blacklist - Trap-based blacklist of domains in spam, phishing, and malware - Lookup Zone: dblack.mail.abusix.zone - Check Now

IBM DNS Blacklist - IBM X-Force Threat Intelligence DNSBL for malicious and suspicious domains - Lookup Zone: dnsbl.cobion.com - Check Now

Lashback - Unsubscribe/opt-out abuse list for domains violating CAN-SPAM rules - Lookup Zone: ubl.unsubscore.com - Check Now

SEM URI - SEM Labs' DNSBL for URIs found in spam and phishing emails - Lookup Zone: uribl.semeon.com - Check Now

SEM URIRED - SEM Labs' DNSBL for high-risk URIs and domains - Lookup Zone: urired.semeon.com - Check Now

SEM FRESH - SEM Labs' DNSBL for newly observed domains and URIs - Lookup Zone: fresh.semeon.com - Check Now

Anonmails DNSBL (Domain) - Community-maintained domain blacklist for abuse and phishing - Lookup Zone: rhsbl.anonmails.de - Check Now

Nordspam DBL - Nordic-focused domain blacklist for spam and abuse - Lookup Zone: dbl.nordspam.com - Check Now

SORBS RHSBL BADCONF - SORBS DNSBL for domains with bad configuration or setup issues - Lookup Zone: badconf.rhsbl.sorbs.net - Check Now

Medium Impact Blocklists

Specialty IP Blacklists

Backscatterer - Detects mail servers that send non-delivery bounces to forged email addresses - Lookup Zone: ips.backscatterer.org - Check Now

CYMRU Bogons - Lists bogon (unallocated/reserved) IP ranges never used for legitimate email - Lookup Zone: v4.fullbogons.cymru.com - Check Now

DroneBL - IPs detected as bots, drones, or open proxies often used for abuse - Lookup Zone: dnsbl.dronebl.org - Check Now

DAN TOR - Lists known TOR exit node IPs - Lookup Zone: tor.dnsbl.sectoor.de - Check Now

DAN TOREXIT - DNSBL for active TOR exit IPs - Lookup Zone: toreexit.dan.me.uk - Check Now

SEM BACKSCATTER - SEM Labs' backscatter detection list - Lookup Zone: backscatter.semeon.com - Check Now

SEM BLACK - SEM Labs' IP blacklist for spam sources - Lookup Zone: black.semeon.com - Check Now

FABELSOURCES - Lists IPs detected as sources of spam, malware, or abuse - Lookup Zone: blackholes.fabel.dk - Check Now

IMP SPAM - IMP SPAM tracks IPs associated with spam and abusive activity - Lookup Zone: dnsbl.imp.ch - Check Now

IMP WORM - IPs involved in worm and virus propagation - Lookup Zone: wormbl.imp.ch - Check Now

Policy and Relay Blacklists

SORBS DUL - SORBS Dynamic User List for dynamic/residential IPs - Lookup Zone: dul.dnsbl.sorbs.net - Check Now

SORBS HTTP - SORBS HTTP blacklist for web-based spam sources - Lookup Zone: http.dnsbl.sorbs.net - Check Now

SORBS SMTP - SORBS SMTP blacklist for mail server abuse - Lookup Zone: smtp.dnsbl.sorbs.net - Check Now

SORBS SOCKS - SORBS SOCKS proxy blacklist - Lookup Zone: socks.dnsbl.sorbs.net - Check Now

SORBS MISC - SORBS miscellaneous abuse blacklist - Lookup Zone: misc.dnsbl.sorbs.net - Check Now

SORBS ZOMBIE - SORBS zombie computer blacklist - Lookup Zone: zombie.dnsbl.sorbs.net - Check Now

SORBS SPAM - SORBS spam blacklist - Lookup Zone: spam.dnsbl.sorbs.net - Check Now

SpamRats DUL - SpamRats Dynamic User List - Lookup Zone: dul.spamrats.com - Check Now

SpamRats DYNIP - SpamRats Dynamic IP blacklist - Lookup Zone: dynip.rothen.com - Check Now

SpamRats NOPTR - SpamRats No PTR record blacklist - Lookup Zone: noptr.spamrats.com - Check Now

SpamRats SPAM - SpamRats spam blacklist - Lookup Zone: spam.spamrats.com - Check Now

SpamRats DYNA - SpamRats dynamic IP blacklist - Lookup Zone: dyna.spamrats.com - Check Now

Regional and Community Blacklists

Korea Services - Korean-focused spam blacklist - Lookup Zone: korea.services.net - Check Now

Manitu - German ISP blacklist for spam and abuse - Lookup Zone: ix.dnsbl.manitu.net - Check Now

Singular - Hungarian university spam blacklist - Lookup Zone: singular.ttk.pte.hu - Check Now

Anonmails - German community spam blacklist - Lookup Zone: spam.dnsbl.anonmails.de - Check Now

SpamSpike - MailSpike spam blacklist - Lookup Zone: z.mailspike.net - Check Now

Low Impact Blocklists

Malware and Exploit Blacklists

Abusix Malware - Abusix malware detection blacklist - Lookup Zone: malware.mail.abusix.zone - Check Now

Abusix Phishing - Abusix phishing detection blacklist - Lookup Zone: phishing.mail.abusix.zone - Check Now

Abusix Exploit - Abusix exploit detection blacklist - Lookup Zone: exploit.mail.abusix.zone - Check Now

Virus RBL JP - Japanese virus blacklist - Lookup Zone: virus.rbl.jp - Check Now

IMP WORM - IMP worm and virus blacklist - Lookup Zone: worrmbl.imp.ch - Check Now

Miscellaneous Operator Blacklists

WoodyNet - WoodyNet spam blacklist - Lookup Zone: woodybl.dnsbl.woodynet.net - Check Now

Cymru Bogons - Cymru bogon IP blacklist - Lookup Zone: bogons.cymru.com - Check Now

CBL - Composite Blocking List - Lookup Zone: cbl.abuseat.org - Check Now

Combined Abuse.ch - Combined abuse.ch blacklists - Lookup Zone: combined.abuse.ch - Check Now

WPBL - WPBL spam blacklist - Lookup Zone: db.wpbl.info - Check Now

UCEPROTECT L2 - UCEPROTECT Level 2 blacklist - Lookup Zone: dnsbl-2.uceprotect.net - Check Now

UCEPROTECT L3 - UCEPROTECT Level 3 blacklist - Lookup Zone: dnsbl-3.uceprotect.net - Check Now

DroneBL - DroneBL botnet blacklist - Lookup Zone: drone.abuse.ch - Check Now

SORBS - SORBS general blacklist - Lookup Zone: dnsbl.sorbs.net - Check Now

SPFBL - SPFBL spam blacklist - Lookup Zone: dnsbl.spfbl.net - Check Now

DUINV - DUINV spam blacklist - Lookup Zone: duinv.aupads.org - Check Now

ORVEDB - ORVEDB spam blacklist - Lookup Zone: orvedb.aupads.org - Check Now

PBL - Policy Block List - Lookup Zone: pbl.spamhaus.org - Check Now

Proxy BL - Proxy blacklist - Lookup Zone: proxy.bl.gweep.ca - Check Now

PSBL - PSBL spam blacklist - Lookup Zone: psbl.surriel.com - Check Now

Relays BL - Relays blacklist - Lookup Zone: relays.bl.gweep.ca - Check Now

Relays Nether - Relays Nether blacklist - Lookup Zone: relays.nether.net - Check Now

SBL - Spamhaus Block List - Lookup Zone: sbl.spamhaus.org - Check Now

XBL - Exploits Block List - Lookup Zone: xbl.spamhaus.org - Check Now