Why is my domain or IP blocked by Spamhaus and how do I resolve it?
Matthew Whittaker
Co-founder & CTO, Suped
Published 14 Jun 2025
Updated 15 Aug 2025
9 min read
Dealing with email deliverability issues can be incredibly frustrating, especially when your emails are being blocked by a major authority like Spamhaus. It can feel like you're sending emails into a black hole, with no idea why they aren't reaching their destination. I've seen many senders grapple with this, and it often comes down to a few core issues, whether it's related to your IP address or your domain itself. Understanding why you've been blocklisted (or blacklisted, as it's often called) is the first critical step toward getting your email flow back on track.
The good news is that most Spamhaus listings have clear reasons and pathways to resolution, though it requires diligent investigation and corrective action. It's not always about outright spamming; sometimes, subtle issues in your sending practices or network configuration can lead to a block. My goal here is to guide you through the typical causes of these blocks and provide a practical approach to resolving them, helping you restore your sender reputation.
What are Spamhaus blocklists and how do they work?
When your domain or IP address is blocked by Spamhaus, it means that your email sending is being flagged as suspicious or harmful by one of the leading global authorities in spam prevention. Spamhaus maintains several blocklists (or blacklists) that internet service providers (ISPs) and email administrators use to filter out unwanted email. If you find yourself on one, it's a serious indicator that something is amiss with your email program.
Spamhaus compiles its blocklists by observing and identifying sources of spam and other malicious email activity. This can range from direct spamming and malware distribution to the hosting of fraudulent content. Each of their blocklists targets a specific type of threat or entity. For instance, the Spamhaus Blocklist (SBL) targets IP addresses involved in sending spam, while the Domain Blocklist (DBL) focuses on domains used in spam messages or malicious websites. Understanding the nuances of these lists is crucial for diagnosis.
A listing on a Spamhaus blocklist (sometimes called a blacklist) can severely impact your email deliverability, causing your legitimate emails to be rejected or routed to spam folders. This is why it's so important to regularly monitor your domain and IP reputation. You can learn more about the different types of these lists in an in-depth guide to email blocklists.
Blocklist Name
What it lists
Common causes
SBL (Spamhaus Blocklist)
IP addresses identified as sending spam or other unsolicited bulk email.
Domain names found in spam or used for malicious purposes (e.g., phishing).
Domain registered by spammers, URL shorteners, domains with poor reputation used in email.
PBL (Policy Blocklist)
IP address ranges that should not be sending unauthenticated email directly to the internet, such as residential IPs.
Sending email from dynamic IP addresses (e.g., home networks), misconfigured mail servers.
XBL (Exploits Blocklist)
IP addresses of compromised PCs or servers infected with malware (e.g., botnets, zombies).
Viruses, worms, trojans, open proxies, insecure web servers.
CSS (Composite Snowshoe Spam)
IP addresses engaged in 'snowshoe spamming' (sending low volumes of spam from many IPs/domains).
Rapid rotation of IPs and domains, sending from many country-specific TLDs, poor sender reputation across multiple IPs.
Common reasons for Spamhaus listings
The primary reasons for getting listed on a Spamhaus blocklist often boil down to practices that compromise email security or adhere to unsolicited sending. One common cause is sending to spam traps, which are email addresses specifically designed to catch spammers. Hitting these indicates issues with your list hygiene or acquisition methods. Another significant factor is having compromised systems (e.g., a server infected with malware) that are inadvertently sending out spam without your knowledge. Even if you're not directly responsible, your IP can be implicated.
Another pervasive issue, especially for those managing multiple clients or campaigns, is a lack of strict consent. If your recipients haven't explicitly opted in to receive your emails, or if your opt-in process is weak, you risk high complaint rates, which contribute to a poor sender reputation. This can quickly lead to a blocklist entry. Spamhaus's policy for the SBL (Spamhaus Blocklist) states it lists IPs under the control of, or used by, spammers and abusers in unsolicited bulk email or other internet-based abuse.You can review their SBL policy here.
Furthermore, certain sending patterns can trigger flags. For example, using numerous subdomains or country-specific TLDs (top-level domains) to send similar mail might appear suspicious, leading to a CSS listing. Similarly, sending marketing emails from residential IP addresses (which should primarily be used for personal internet access) can trigger a PBL listing. It’s important to remember that the age of your domain can also play a role, with newer domains sometimes receiving less leeway due to potential for abuse. For more details on this, see what causes Spamhaus blacklisting.
Common pitfalls
Sending to purchased lists: These often contain spam traps or outdated, unengaged addresses leading to high bounce and complaint rates.
Poor list hygiene: Not regularly cleaning your subscriber list can result in hitting spam traps or sending to invalid addresses.
Compromised accounts: Spammers can exploit vulnerabilities in your system to send unsolicited mail, unknowingly to you.
Lack of proper authentication: Missing or misconfigured SPF, DKIM, or DMARC records can make your emails appear suspicious.
Pinpointing the source of the problem
Once you've confirmed your IP or domain is listed on Spamhaus (you can use their IP and Domain Reputation Checker), the next step is to pinpoint the exact reason. Spamhaus listings often provide a general reason, but you'll need to dig deeper into your own email logs and sending practices. This process can be challenging, especially if you manage mail for multiple clients or have a complex sending infrastructure. It’s not about finding out which user reported you to Spamhaus (as users don't directly report to them); rather, it's about identifying the activity that triggered their automated systems or spam traps.
Start by reviewing your email sending logs for unusual activity, spikes in volume, or high bounce rates, especially for unknown users. Pay close attention to feedback loop (FBL) complaints. FBLs indicate that recipients are marking your emails as spam, which is a strong signal of unsolicited mail. While FBLs don't directly tell you which user caused a Spamhaus listing, they serve as a proxy for direct complaints and highlight problematic lists or campaigns.
If you are an ESP or manage mail for others, you might need to audit your client base. Look for clients sending to non-opt-in lists or engaging in aggressive sending practices. Sometimes, the issue isn't malicious intent but simply poor email marketing hygiene. Identifying these problematic customers and stopping their problematic sending is the most effective way to address the root cause of the block. For a broader view, consider reading how to check Spamhaus for your IP address.
Diagnosing the problem
Check Spamhaus listing details: Use their lookup tool to see which specific blocklist your IP/domain is on and the brief reason provided.
Review email logs: Look for unusual sending patterns, spikes, sudden increases in bounce rates, or messages flagged as spam.
Analyze FBL data: Feedback loops provide insights into which recipients are complaining and the campaigns causing issues.
Identifying the root cause
Customer audit: If you're an ESP, rank customers by FBL complaints and require proof of consent for suspicious sending.
System scan: Scan your servers and networks for malware, open relays, or other vulnerabilities that could be exploited.
Review sending practices: Ensure all email lists are opt-in, properly segmented, and regularly cleaned of inactive or invalid addresses.
Delisting and prevention strategies
Once you've identified and fixed the underlying issue that led to the Spamhaus block, you can then proceed with the delisting process. Spamhaus generally requires you to resolve the problem before they will consider removing your listing. This is critical because if the root cause isn't addressed, you'll likely find yourself relisted shortly after removal. The exact delisting steps vary slightly depending on which Spamhaus blocklist you are on, but they typically involve using the Spamhaus Blocklist Removal Center (now the IP and Domain Reputation Checker) to submit your request.
For IP listings, you'll enter your IP address into their tool, which will then guide you through the specific reasons for the listing and the necessary steps for removal. For domains, you'll do the same for your domain. Be prepared to provide evidence that the issue has been resolved, such as malware removal reports, changes to sending practices, or improved list hygiene. It's often a good idea to communicate with your Internet Service Provider (ISP) or hosting provider, as they may need to assist with IP delisting or provide insights into network-level issues. You can find more comprehensive advice on how to get delisted from Spamhaus.
Prevention is always better than cure. To avoid future blocklists or blacklists (whether on Spamhaus or other lists), implement robust email practices. This includes maintaining clean, opt-in mailing lists, regularly monitoring your email sending infrastructure for vulnerabilities, and ensuring your email authentication records (SPF, DKIM, DMARC) are correctly configured. Proactive measures will safeguard your sender reputation and ensure your emails reach their intended inboxes.
Example: Checking an IP against Spamhaus ZENDNS
Check if your IP is listed on Spamhaus:
nslookup 2.0.0.127.zen.spamhaus.org
Views from the trenches
Best practices
Maintain strict opt-in processes for all email lists to ensure recipients genuinely want your mail.
Regularly clean your email lists to remove inactive users, bounces, and potential spam traps.
Implement and correctly configure email authentication protocols like SPF, DKIM, and DMARC.
Monitor your sending reputation daily using available tools to catch issues early.
Segment your sending by reputation to isolate high-risk email streams from your main volume.
Common pitfalls
Sending to non-permission-based lists, such as purchased or scraped email addresses.
Ignoring feedback loop (FBL) complaints, which indicate recipients are marking your emails as spam.
Failing to regularly scan your mail servers for malware or open relays that could be exploited.
Using a single root domain with many subdomains or country-specific TLDs for varied campaigns.
Delaying action when a listing occurs, allowing the problem to worsen and affect more email.
Expert tips
If your IP is listed, check if it's due to a compromised system or abusive customer activity.
When dealing with multiple clients, stack them by FBL complaints to identify problematic senders.
For ESPs, it's crucial to verify consent for customers sending
cold emails
or to non-permission lists.
Expert view
Expert from Email Geeks says: You need to understand who is sending mail on your behalf and how recipients are opting in, as this is often the starting point for a listing.
2020-08-11 - Email Geeks
Marketer view
Marketer from Email Geeks says: If you're sending from multiple subdomains of the same root domain, this pattern can trigger a CSS listing if spam traps are hit.
2020-08-11 - Email Geeks
Restoring and maintaining your email reputation
Being blocked by Spamhaus is a clear signal that your email sending practices need immediate attention. Whether it's a compromised system, poor list hygiene, or issues with consent, understanding the precise reason for the listing is paramount. Once identified, implementing corrective measures and following the delisting process diligently will help restore your sender reputation.
Beyond resolving current issues, adopting a proactive stance on email deliverability is key. This involves continuous monitoring, maintaining clean lists, and ensuring strong email authentication. By doing so, you can minimize the risk of future blocklistings (or blacklistings) and ensure your email marketing efforts remain effective, reaching your audience reliably.
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
TechTheft
SBL (Spamhaus Blocklist)
