How to fix a Spamhaus CBL listing when using multiple ESPs and Bluehost?
Matthew Whittaker
Co-founder & CTO, Suped
Published 21 Apr 2025
Updated 15 Aug 2025
9 min read
Dealing with a Spamhaus CBL listing is a serious challenge, especially when juggling multiple email service providers (ESPs) and self-managed infrastructure like Bluehost. I have seen many situations where a client, despite having a legitimate business, finds their email campaigns landing in junk folders because their IPs are on a major blocklist. This often stems from a lack of awareness regarding email marketing best practices and technical configurations. The Composite Blocklist (CBL) specifically targets IP addresses involved in sending spam or hosting malicious content, which means the issue is likely rooted in a compromised system or misconfigured server, rather than content-related spam. When multiple sending platforms, such as Ontraport, ActiveCampaign, Infusionsoft, and even Mailgun with third-party software like Mailwizz, are in play, diagnosing and fixing the problem becomes even more complex. My goal is to guide you through identifying the root causes and implementing effective solutions to get your IPs delisted and restore your email deliverability.
The immediate consequence of a CBL listing is a significant drop in email deliverability, as most major mailbox providers heavily rely on Spamhaus data to filter incoming mail. This impacts everything from transactional emails to marketing campaigns. Simply moving to new IPs or ESPs without addressing the underlying problem often leads to being re-listed, sometimes even triggering a “snow shoe” designation, which makes future delisting efforts even harder. It is crucial to approach this with a clear strategy, focusing on identifying vulnerabilities and implementing robust security measures. This guide outlines the steps needed to understand, address, and resolve a Spamhaus CBL listing, particularly in environments with diverse email sending infrastructure and Bluehost servers.
The Spamhaus CBL is one of the most respected and widely used IP address blocklists (or blacklists). It primarily lists IP addresses that have been observed sending spam, acting as open relays, or being part of botnets. Unlike other blocklists that might focus on sender reputation or content, the CBL is highly technical, targeting compromised systems. If your IPs are listed, it signals that one of your machines, or a client's machine on your network, is likely compromised or misconfigured and is actively emitting spam or malicious traffic.
In a scenario involving Bluehost servers, particularly virtual private servers (VPS), the responsibility for these issues often falls directly on the client. Even if you're using other ESPs for marketing emails, the CBL listing usually points to a core infrastructure problem, such as compromised web servers, outdated CMS installations, or misconfigured mail relays on your Bluehost IP addresses. The reverse DNS lookup (rDNS) often resolves directly to Bluehost, confirming that the issue originates from a server under that hosting provider.
Understanding what causes Spamhaus blacklisting is the first step. For CBL, it is almost always due to an IP address emitting spam, often without the owner's knowledge. This typically happens because a server or device on that IP has been compromised, or software (like a content management system, web application, or even an IoT device) has vulnerabilities that spammers exploit to send unsolicited emails. This type of listing is less about poor email marketing practices and more about system security.
Understanding CBL listings
The Spamhaus Composite Blocklist (CBL) focuses on IP addresses that exhibit characteristics of compromised systems sending spam. It is not about content or sender reputation, but rather the observed malicious activity directly from an IP. If your IP is on the CBL, it's a strong indicator of a security breach or misconfiguration on the server associated with that IP.
The challenge of multiple ESPs and Bluehost
Managing email sending across multiple ESPs (e.g., Ontraport, ActiveCampaign, Infusionsoft, Mailgun) and an in-house Bluehost solution creates a fragmented email ecosystem. Each platform has its own IP addresses and reputation, making it difficult to pinpoint the source of a blocklist (or blacklist) issue. When a CBL listing occurs, it's highly probable that the compromised IP belongs to your Bluehost server, as this is typically where less-managed or custom setups reside. The other ESPs usually have more robust security measures and monitor their IPs closely.
The nature of your Bluehost setup, whether it is a shared hosting environment, a managed VPS, or an unmanaged VPS, significantly impacts how you should proceed. If it's a shared hosting environment, Bluehost will likely be responsible for security and delisting. However, if it is a VPS, you or your IT team will have more control, and thus more responsibility for securing the server and initiating the delisting process. Regardless, engaging with Bluehost support is a critical first step, as they can provide insights into server activity and assist with network-level issues. I've found that VPS clients often receive a higher level of support compared to shared hosting users.
In-house bluehost server
Vulnerability focus: Often indicates a compromised system (e.g., website, outdated software, insecure configurations) on the Bluehost IP, leading to spam emission.
Resolution responsibility: Depends on the Bluehost service level (shared, managed VPS, unmanaged VPS). More control means more responsibility.
Technical investigation: Requires checking server logs, outbound mail queues, and network configurations.
Fragmented sending
Diagnosis difficulty: Hard to pinpoint the exact source of a blocklist among multiple IPs and platforms.
Inconsistent practices: Varying email practices across ESPs can lead to different deliverability outcomes.
Reputation dilution: Spreading sending volume can prevent a single IP from building strong, consistent reputation.
Centralized sending
Simplified troubleshooting: Easier to identify and resolve issues when all email traffic flows through one primary ESP.
Consistent policies: Ensures all sending adheres to a single set of best practices and configurations.
Stronger reputation: Concentrated volume helps build and maintain a robust IP and domain reputation.
Diagnosing the root cause and initial steps
The first step is to definitively understand why your IPs are listed on the Spamhaus CBL. You can check the specific listing details by visiting the Spamhaus CBL lookup page and entering the listed IP addresses. The lookup results will provide detailed information about why the IP was listed, often pointing to specific malware, botnet activity, or open relays (e.g., a MikroTik router vulnerability, as sometimes seen). This information is crucial for your IT team or Bluehost to begin their investigation.
Once you have the reason, your IT team needs to perform a thorough audit of the affected Bluehost server. This includes checking server logs for unusual activity, scanning for malware, reviewing outbound mail queues for unauthorized mail, and verifying network configurations. Pay close attention to mail sending ports, particularly if port 25 is open for outbound mail without proper authentication, as this is a common vector for abuse. Port 587, the submission port, should ideally be used for authenticated outbound mail.
Common commands for diagnosing mail server issuesBASH
Do not rush into requesting delisting before fully resolving the issue. Spamhaus (and other blocklists) are unlikely to be forgiving if an IP is re-listed due to the same problem. This means stopping all malicious activity first, which might involve temporarily halting email sending from the affected IPs or isolating the compromised server. While working on the technical fix, review your email acquisition processes to ensure there are no loopholes that could introduce spam traps or unengaged users to your lists, as this often leads to reputation problems even if not directly causing a CBL listing. If you need a more general understanding of how to proceed, consider reading what to do if listed in Spamhaus.
Implementing solutions and delisting
Once the root cause is identified, the immediate action is to secure the compromised system. This could involve updating all software, patching vulnerabilities, removing malware, changing all passwords, and ensuring no unauthorized mail relays are active. For Bluehost VPS users, this means actively engaging with their IT team to implement these changes. If Bluehost provides managed services, leverage their support to resolve the server-side issues.
For CBL listings, delisting is often automatic once the malicious activity ceases, but you can also initiate a manual removal request through the Spamhaus delisting portal. Be prepared to describe the steps taken to fix the issue. Avoid the temptation to abandon the listed IPs and move to new ones or new ESPs without resolving the core problem. This practice, known as “snow-shoeing”, can lead to future, more severe blocklistings and damage your sending reputation across all domains. You can get additional help by learning how to get help with a Spamhaus listing.
Snow-shoeing warning
Resorting to frequently moving IPs or domains to evade blocklists (also known as “snow-shoeing”) is a red flag to blocklist operators and mailbox providers. This tactic rarely works long-term and can severely damage your overall sender reputation, making it harder to reach the inbox in the future. Focus on fixing the root problem instead.
Long-term, implement robust security measures and monitor your sending practices across all platforms. Consolidate your email sending where possible to streamline management and build a stronger, more consistent sending reputation. Continuously validate your email lists, remove unengaged subscribers, and ensure all opt-in processes are clear and compliant. Proactive list hygiene and adherence to email sending best practices are essential for preventing future blocklistings and ensuring high email deliverability. Consider using an email blocklist checker regularly.
Views from the trenches
Best practices
Conduct a comprehensive security audit of your entire email infrastructure, including Bluehost servers and all ESP accounts, to identify vulnerabilities.
Consolidate email sending to fewer, more reputable ESPs to simplify management and improve overall sender reputation.
Implement strict list hygiene practices, including regular validation and removal of unengaged or invalid email addresses.
Ensure all email authentication records (SPF, DKIM, DMARC) are correctly configured across all domains and sending services.
Common pitfalls
Ignoring the root cause of the listing and attempting to bypass it by constantly switching IPs or domains, leading to 'snow-shoe' spammer classification.
Neglecting to engage with your hosting provider's (e.g., Bluehost) support or IT team to address server-side security issues.
Failing to monitor outbound mail queues and server logs, allowing compromised systems to continue sending spam unnoticed.
Using outdated or insecure software on your servers, creating easy entry points for malicious actors.
Expert tips
For CBL listings, the problem is almost always technical: a compromised server, open relay, or botnet activity.
Always fix the underlying issue before requesting delisting; otherwise, you'll likely be re-listed.
Engage with your hosting provider's (Bluehost) IT team. Ask whether it's a managed VPS or if they administer the server.
If your client is legitimately sending email, ensure their email acquisition process is clean and their lists are healthy.
Expert view
Expert from Email Geeks says that mailing from multiple ESPs can indicate deeper underlying issues in a client's email practices that extend beyond simple technical fixes.
2020-12-08 - Email Geeks
Expert view
Expert from Email Geeks says that changing ESPs or domains without resolving the root problem risks a 'snow shoe' spammer listing, making future delisting much harder.
2020-12-08 - Email Geeks
Final thoughts
Navigating a Spamhaus CBL listing, especially with a complex setup involving multiple ESPs and Bluehost servers, requires a methodical approach. The core issue is almost always a technical vulnerability leading to unwanted email traffic. By accurately diagnosing the problem, securing your systems, and working collaboratively with your hosting provider and IT team, you can effectively resolve the listing and prevent recurrence. Remember, long-term email deliverability success hinges on strong security, consistent best practices, and a clear understanding of your email sending infrastructure.
Avoid quick fixes like simply switching IPs or domains, as these can exacerbate the problem. Instead, invest in thoroughly cleaning up compromised systems, improving your email acquisition processes, and ensuring proper authentication and list hygiene. This holistic approach will not only get you off the CBL but also build a more resilient and reputable email program for the future. Consider leveraging tools and services for blocklist monitoring to stay ahead of potential issues.
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
Bluehost IP, leading to spam emission.
