Spamhaus Zen: What Is It & How To Fix ASAP

Listed on Spamhaus Zen? Relax and follow our quick guide. Find out why you landed there, how to be delisted and tips to avoid being blacklisted again.

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What is Spamhaus Zen?

The Spamhaus ZEN blacklist combines all Spamhaus IP-based blacklists into one powerful and comprehensive blocklist to make the IP lookup faster and simpler.

Spamhaus ZEN is a database of IP addresses that are associated with spam or malicious email traffic in some way.

The ZEN blacklist groups 4 Spamhaus blocklists together: SBL, SBLCSS, XBL, and PBL.

In other words, If you’re listed in ZEN, you’ll see a listing for ZEN and for one or more of the included Spamhaus block lists.

Make sure to check on which blocklist(s) you have been listed to better understand the causes. To see if you’re listed on any of Spamhaus lists, simply check here.   

SBL (Spamhaus Block List)

The Spamhaus Block List (SBL) is a database of addresses from which Spamhaus does not recommend the acceptance of emails because Spamhaus deems that those IP addresses have been involved in the sending, hosting, or origination of Unsolicited Bulk Email.

SBLCSS Block list

The Spamhaus SBLCSS is a list of IP addresses that are marked to have sent low-reputation emails. Specifically, it lists those that have:

  • Poor list hygiene / spam traps.
  • Sent emails with indications of abuse or an unsolicited nature
  • Sent bad emails caused by a compromise

SBLCSS lists IPs based on multiple events and heuristics.

XBL (Exploits Block list)

The Exploits Block List (XBL) from Spamhaus is a real-time database consisting of IPs from hijacked computers. The devices of these addresses are those that have been infected by illegal third-party exploits such as worms with built-in spam engines, open proxies, and Trojan horse varieties.

PBL (Policy Block list)

Then, there’s also the Spamhaus Policy Block List (PBL) which is a DNSBL usage database containing end-user IP address ranges. These addresses are flagged to not deliver unauthenticated emails to mail servers with the exception of those supplied specifically by an internet service provider for customer use.

Both static and dynamic IP address ranges are listed in the PBL so long as they qualify for free use. These aren’t allowed to send emails directly to a third-party mail server.

The main causes of being listed on Spamhaus Zen and its blocklists

Cause 1: Spam traps

Spamhaus is designed to identify spammers through the use of special, confidential email addresses known as "spam traps." A spam trap is an email address that is not in active use. Despite being publicly available, these addresses are often used to compile and sell email lists. If an individual or organization starts sending emails to such a compiled and often outdated list, Spamhaus will mark them as a spammer who has not obtained consent from the recipients.

Cause 2: High complaint rate

Even if you are not sending spam, you may still find yourself on a blacklist due to recipients marking your emails as spam. When a recipient flags your email as spam, the Spamhaus system receives a notification. If multiple complaints are received, you will eventually be added to a Spamhaus blacklist.

Cause 3: Rapid increase in list size

To avoid being placed on a list on Spamhaus, it's important to monitor the size of your email list. Sudden spikes in the number of emails you send, such as going from a few per day to hundreds within a short period, can raise red flags with ISPs. They may suspect that the email list was purchased, making it potentially spam-like and dangerous. It's advisable to maintain a consistent and gradual growth in the size of your contact list.

Cause 4: Using the same IP address by different people

It's possible that multiple users share a single public IP address through a technique called NAT. If you have recently shared an IP address with someone whose machine sent spam, then your IP address may have been put on a blocklist.

Cause 5: Malware on your email server

You have contracted a virus or malware that is operating a botnet, either on your mail server on a workstation behind the NAT.

How to remove your IP from Spamhaus Zen?

1. First, run a blocklist check with your IP

The first step is to check if your IP is listed in any of the Spamhaus blocklists and, if yes, which one(s).

Go to the Spamhaus Check page, enter your IP address and do a lookup.

If the domain reputation checker/blocklist removal center helps you confirm that your IP address exists on the blocklist, you may see your search result come back with a warning message.

Click Show Details to find more details that might help explain and fix the issue. If you are using a shared IP address (and another user is responsible for the listing) or don’t have access to your email servers, you'll need to contact your hosting / email provider / ISP to have the issue fixed.

2. Find out the block reason

Spamhaus has different blocklists that block IP addresses for different reasons. However, if they exist in XBL or SBL, that may identify a security problem. To investigate the reason behind it, look through your server logs. They can reveal data about suspicious or malicious activity inside and outside your network.

The Spamhaus IP domain and reputation checker further facilitates the investigation by helping to identify what the issue might be and why your IP is on an XBL, SBL or another list on Spamhaus.

If you checked your log files, found the problem and fixed it, you can send IP address removal requests by ticking a box and clicking Next Steps.

3. Request Spamhaus blocklist removal

To delist from Spamhaus and petition for IP address removal, fill out the form to provide your contact data and click Submit.

When Spamhaus accepts your removal form, it will process it immediately. However, the delist from Spamhaus may take a few minutes up to 24 hours. If your IP address is still on the list after 24 hours, contact Spamhaus’ technical account manager for removal assistance.

How to Avoid Being Listed in Spamhaus Zen

To avoid being listed on the Spamhaus Zen blacklist in the future, it's crucial to follow best practices for email deliverability. Some of the most effective measures include:

1. Minimize your risk of sending emails to spam traps

  • Don't buy lists : they can contain spam traps, people with high complaint rates etc. Bad idea.
  • Don't collect email addresses all over the internet:
  • For marketing / newsletters / transactional emails, your contacts should only come from people who opted in.
  • For a cold email sending activity: get your email list from LinkedIn using a scraping tool like Evaboot.

2. Minimize your risk of having spam complaints

  • Obtaining explicit consent from recipients before sending them emails and honoring opt-out requests promptly (For marketing / newsletters / transactional emails)
  • Providing a clear and easy-to-use unsubscribe link in all emails.

3. Monitor your sender reputation

  • Regularly monitoring your IP reputation and deliverability to detect and resolve issues quickly.
  • Use a solution like MailReach to help your follow your reputation and raise it. See below for more details.

4. Get properly authenticated and secured

  • Set up the SPF, DKIM, and DMARC records to demonstrate that you're a legitimate sender.
  • For those who have their own mail servers, secure your servers to protect them from malware or bots that send fake emails, which can hijack your IP address and easily cause blocklisting.

Important: Test your deliverability now, it's free and takes 1 minute

You need to check how your deliverability is doing and take action if needed. ‍

To get your deliverability score and find out where your emails land on the major providers, you can use MailReach’s Free Email Spam Test. Most of the other existing tools are biased and/or not reliable to properly measure your inbox placement. 

Basically, you simply have to send an email (in real sending conditions) to a list of 31 inboxes given by MailReach and we’ll give you a detailed report on your deliverability including all the things you can improve to land more in inbox. 

You get a score out of 10 and a list of checks (content, spam words, links, tracking, blacklists and many more)

Spamhaus Zen : MailReach spam test report
MailReach's Email Spam Test to check the impact of the Spamhaus listing.

Monitor and raise your sender reputation with MailReach

To have a great deliverability and deliver all your emails to the inbox of your recipients, you need to have a good sender reputation. Your sender reputation is mostly influenced by how your recipients react to your emails. 

In other words, the more positive engagement you get on your emails, the more likely you are to reach the inbox. 

By getting positive interactions to your emails (openings, positive replies, stars, removing your emails from spam) it teaches the major mailbox providers, Google and Microsoft to put your emails in the inbox of their users. 

That’s the job of MailReach’s email warm up service : generating a perfect email activity to your inbox by starting conversations with a network of thousands of inboxes. Each of your warming emails are opened, replied positively, marked as important and removed from spam. It raises your sender reputation and, in turn, your deliverability. 

Spamhaus Zen : email warmer dashboard
MailReach's email warmer to improve your deliverability - Spamhaus Zen

Final words about Spamhaus Zen

In conclusion, Spamhaus Zen is a critical blacklist that can have a significant impact on your email deliverability. If your IP address is listed, it's essential to identify and resolve the issue and follow best practices for email deliverability to prevent future listings. By taking these steps, you can protect your reputation and maintain a high deliverability for your business.

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