Have you ever sent an important email to find out later that the recipient never received it? Instead of landing in their inbox, your email ended up in the spam folder, or worse, lost in the abyss of a blacklisted email domain. This painful scenario is common for businesses with a poor sender reputation. If your emails get marked as spam or go missing, it can hurt communication with your customers and prospects and undermine your bottom line. This article will offer insights to help you avoid these problems by ensuring your emails reach inboxes reliably, restoring your sender reputation if blacklisted, fix email reputation, and preventing lost communication.

Inframail’s email infrastructure solution can help you achieve these goals with ease. By improving your email deliverability, we can help you avoid lost communication, and quickly restore your sender reputation if your emails are ever blacklisted.

Table of Contents

• What Does “Blacklisted Email” Mean?

• How Do Email Blacklists Work?

• How to Find Out if Your Email Is Blacklisted

• How to Get Off Email Blacklists?

• Start Buying Domains Now and Set Up Your Email Infrastructure Today

What Does “Blacklisted Email” Mean?

An email blacklist (or ‘blocklist’) is a collection of domains and/or IP addresses blocked from sending emails to email users because of spam activity. There are different kinds of blacklists including: 

• Webmail providers run internal ones (Gmail, Outlook, etc)

• Security companies run external ones (Proofpoint, Barracuda, Cloudmark, etc).

• Those are managed by non-profit organisations (Spamhaus, SURBL, etc.). 

My IP/Domain's Been Blacklisted, How Did This Happen? 

ISPs (Internet Service Providers) like Yahoo, Gmail, and Outlook use spam filters to decide whether an email is: 

• Delivered

• Flagged as suspicious

• Rejected entirely

Getting your emails past spam filters is crucial in email marketing to prevent your work ending up in the junk folder or worse, on an email blacklist! If you wind up on an email blacklist, this means your IP or domain has appeared as if engaging in spam-related activity. The definition of spam varies according to different ISPs and blacklist vendors. 

How to Prevent Blacklisting and Maintain Email Deliverability

While each blacklist has its own set of rules and policies to determine spam, here are some of the typical reasons for getting blacklisted:

Poor Email Hygiene

Failing to maintain a clean email list increases the likelihood of sending messages to invalid or inactive addresses. This wastes resources and damages your sender reputation, signaling poor list management to email providers. For example, you run an online pet supplies store and send weekly newsletters. Your email database accumulates outdated or incorrectly entered addresses without regular list maintenance. As a result, your emails bounce frequently or get marked as spam by disengaged recipients. Over time, these negative signals trigger spam filters, increasing the risk of your domain being blacklisted by email providers, ultimately reducing deliverability and harming your marketing efforts.

High Email Bounce Rates

A high volume of bounced emails signals to Internet Service Providers (ISPs) that a sender may not verify their email list. Without proper validation, senders risk being flagged as spammers. For instance, imagine a small business launching an email campaign without first cleaning and verifying its contact list. Many emails bounce back due to outdated or incorrect addresses. This elevated bounce rate alerts ISPs to poor list management, increasing the likelihood of the domain being classified as spammy. As a result, future emails may be blocked or sent directly to spam folders, significantly hindering deliverability and outreach efforts.

A Lot Of Spam Reports

When recipients repeatedly mark your emails as spam, it directly impacts your sender reputation. A high volume of spam complaints can trigger automated systems to classify your emails as unwanted, increasing the risk of blacklisting. For example, imagine a health and wellness blog enthusiastically launching its newsletter to a broad audience. Despite good intentions, many recipients, either uninterested or unaware they signed up—flag the emails as spam. This surge in complaints damages the blog’s sender score, prompting ISPs to categorize future emails as spam. As a result, the blog risks blacklisting, which can severely impact email deliverability and audience engagement.

Sending Emails To Spam Traps

Sending emails to spam trap addresses signals to email service providers that your list may be poorly managed or sourced unethically. For example, imagine a marketing team eager to expand its reach, purchasing an email list and sending promotional content. Unbeknownst to them, the list contains several spam trap addresses—email addresses used by providers to identify spammers. When these traps receive emails, they raise red flags, suggesting the list was irresponsibly obtained. As a result, the team’s domain may be flagged, damaging its sender reputation and severely impacting email deliverability.

Too Many Outbound Emails

Sudden spikes in email activity can appear suspicious, as it resembles behaviors typical of spammers. Maintaining a consistent and reasonable email-sending pattern is crucial.

Creating Poor Or Spammy Content

Overly promotional content, lacks relevance, or contains spammy keywords can trigger email filters. Effective content should be engaging, relevant, and provide value to the reader.

Hacked Or Compromised Email Account 

An account a malicious actor has taken over can send out large amounts of spam. Such activities tarnish the reputation of the email address and can lead to immediate blacklisting. Any other behavior considered suspicious (a high volume of hard bounces, too many emails sent within a certain period, technical standards not being met) 

How ISPs Use Blacklists in Email Filtering

Spamhaus, one of the most well-known blacklist operators, provides a visual guide to illustrate how blacklists interact with emails during the delivery process. When you send an email (Sender), it is received by an Internet Service Provider (ISP) (Receiver), which evaluates its legitimacy. If the ISP utilizes a blacklist, the sender’s IP address is checked against it. The email then undergoes additional filtering to assess compliance with the ISP’s policies. It is delivered to the recipient’s inbox if it passes these checks. If it fails, it may be flagged as spam or rejected entirely. While blacklists play a role in this process, the final decision depends on the ISP’s broader filtering mechanisms and policies.

How Does An Email Blacklist Affect Your Business? 

Blacklisting can severely impact an email marketing campaign, cutting off: 

• Access to new leads from surveys

• Website activity

• Marketing service providers

More critically, it can prevent communication with long-time, loyal customers who rely on your content. This loss could significantly affect revenue, depending on the platform that blacklists you. Blacklisting directly affects deliverability rates, with varying degrees of impact. A minor drop may go unnoticed, but a significant decline—especially with frequent delivery failures—could lead to being blocked by major providers like Google. If that happens, immediate action is crucial. A spike in returned emails is often an early warning sign of blacklisting. If this issue persists, it’s essential to investigate and resolve it before further damage occurs.

Related Reading

• Blacklist Removal
• IP Address Reputation

How Do Email Blacklists Work?

What Happens When An Email Gets Blacklisted? 

A blacklist serves as a reference point for mail servers to assess a domain’s email history and reputation. If you engage in email activity perceived as spammy, malicious, or unsolicited, you risk being added to a blacklist. When you send an email, the recipient’s server checks your IP address against multiple DNS blacklists. If your IP isn’t listed, the ISP proceeds with additional security checks to determine where to place your email. If your IP matches an entry on a blacklist, the ISP may block the message entirely or reroute it to the spam folder.

How to Prevent Accidental Blacklisting and Maintain a Positive Sender Reputation

Blacklists function as a safeguard for the broader internet, acting as a "No Entry" list based on adverse reports from other mail servers. While they are just one factor in email deliverability, being listed can have an immediate and severe impact. For example, if an email service provider consults a list like the Spamhaus Block List, any email from a flagged IP address will be marked as spam or blocked. Although blacklists help protect users from unwanted emails, legitimate senders can sometimes end up on these lists by mistake.

Types of Email Blacklists: Which One Did You Get On?

The email landscape features various types of blacklists, each serving a unique purpose in maintaining security and filtering spam:

1. IP Blacklists: These target specific IP addresses flagged for sending spam. If an email address sends too many unsolicited messages, the associated IP can be blacklisted, blocking future emails.

2. Domain Blacklists: These focus on the domain part of an email address. If a domain is known for sending spam, all emails from that domain may be blocked.

3. Public Blacklists: Accessible to anyone, these lists are commonly used by email service providers to filter spam. Being reported as spam, receiving multiple user complaints, or landing in a spam trap can lead to being listed here.

4. Private Blacklists: Managed by individual organizations for internal use, these blacklists are not publicly accessible. Getting on one typically occurs through direct interactions with that organization, like failed transactions or other negative behaviors.

5. Spam Firewalls: These dynamic systems block emails in real-time based on identified spammy content or behaviors. They adjust their filtering criteria based on emerging spam trends.

Each type of blacklist helps protect users from unwanted or harmful emails, but can also inadvertently affect legitimate senders if not appropriately managed.

The Most Popular Email Blacklists

There are over 300 known email blacklists available, each with its own impact on email deliverability. Some blacklists have a more significant effect than others, depending on their scope and methodology. Below are some of the most common blacklists, categorized by their focus, and a brief explanation of how they work:

1. UCEPROTECTL1 (IP-based): Targets individual IP addresses flagged for sending spam. IPs are listed when they send messages to spam traps monitored by this blacklist.

2. UCEPROTECTL2 (IP-based): Lists entire ISPs if a large portion of their IP range appears on UCEPROTECTL1, indicating a widespread issue with spam from that provider.

3. UCEPROTECTL3 (Spam-based): Lists entire countries or large networks when spam is detected across multiple ISPs in a region, based on UCEPROTECTL2 listings.

4. SORBS (Public/IP-based): Focuses on servers and IP addresses reported as sources of spam, open relays, or vulnerable to exploitation by spammers.

5. Suomispam (IP-based): This tool targets IP addresses involved in sending spam to Finnish email users or originating from Finland, using user reports and spam traps.

6. Spamhaus Block List (SBL) (Public/IP-based): A respected blacklist that includes IP addresses identified as sources of spam, based on thorough investigations and user reports.

7. Truncate (Spam-based): Automatically lists aggressive spam sources using real-time analysis of spam reports and patterns.

8. Barracuda (Public/IP-based): This service maintains a reputation system for IPs based on spam and malicious activity reports from its user network.

9. SpamCop (Public/IP-based): This service allows users to report spam, which SpamCop uses to identify and list offending IP addresses. The listings are dynamic, reflecting recent reports.

10. SpamRATS (Public/IP-based): This service focuses on IP addresses linked to spamming, especially those from compromised servers or unauthorized sources.

11. Passive Spam Block List (PBSL) (IP-based): This list targets IPs sending low-engagement emails, utilizing spam traps and feedback to identify offenders.

12. Exploits Block List (IP-based): This list identifies IP addresses compromised by malware or viruses and used to send spam or malicious content.

13. ZEN Spamhaus (IP-based) combines several Spamhaus lists to provide a comprehensive view of IP addresses involved in spamming or hosting malicious sites.

14. WPBL (Private): A community-driven blacklist that gathers reports of websites and IPs linked to spam activities.

15. MultiRBL (Multi-DNS-based): Aggregates data from multiple blacklists to offer a broad analysis of potential spam sources.

16. SURBL (Spam-based): This method focuses on URLs within emails associated with phishing, malware, or spam content, helping block harmful messages.

17. Invaluement (Spam-based): Specializes in catching elusive spam that evades conventional filters through sophisticated analysis.

18. SenderScore (IP-based): This service provides email senders with a reputation score based on sending behavior, spam complaints, and sending volume.

19. Senderbase: Like SenderScore, domains and IP addresses are evaluated to rate their email-sending practices.

These blacklists contribute significantly to the efforts of filtering spam and maintaining email hygiene across the internet. Legitimate senders sometimes end up on these lists, severely impacting their email deliverability.

Related Reading

• How to Improve IP Reputation
• Google Blacklist Removal
• How to Get Off Email Blacklist
• Blacklist Removal Tool

How to Find Out if Your Email Is Blacklisted

Email blacklists are databases of IP addresses or domains that have a reputation for sending spam or unsolicited emails. If your address is on a blacklist, it might be that your emails are blocked altogether, or they are being sent to spam folders. Either way, it’s not a good position to be in. 

Check for Blacklist Status 

To check if your address is blacklisted, follow these steps: 

• Look for signs you’re on a blacklist. 

• Check the actual blacklist status. 

• Fix any issues causing the blacklist status. 

• Request removal from the blacklist. 

Signs You’re on a Blacklist 

Understanding whether your email has landed on a blacklist means you have to keep an eye on specific indicators – such as unusually low deliverability rates, spikes in bounce rates, or explicit notifications from email services indicating that your email has been blacklisted. 

Low Deliverability Rate 

A low deliverability rate might mean your emails are being blocked or sent to spam folders, which can happen if your email address or domain is blacklisted. Analyze your email campaign reports for consistent drops in deliverability. Tools within your email service provider can offer insights. 

Spike in Bounce Rates 

A high bounce rate, especially with hard bounces (emails returned due to invalid addresses), may signal that your sending practices are problematic, potentially leading to blacklisting. Monitor your email bounce reports closely. A sudden increase in bounces might require further investigation using online blacklist-checking tools. 

Email Service Notifications 

Receiving a direct notification or seeing warnings in your email platform’s reports suggests you’ve been added to a blacklist. Upon receiving a notification, visit blacklist monitoring websites such as MXToolBox or MultiRBL. Enter your domain or IP address to search across various blacklist databases. 

Investigating Your Blacklist Status 

To investigate further, you can try out some of the following methods. 

Send a Test Email 

There are plenty of platforms where you can send test emails to see how they perform and whether they land in the inbox or spam folder. These services are excellent for helping you understand your email deliverability rates and make necessary adjustments to improve open rates. 

Use an Email Monitoring Tool 

Because blacklists are such a common frustration for email marketers of all types, there are plenty of tools that can do the heavy lifting for you by continuously scanning all the significant blacklists to see if your email is listed. Warmup Inbox also includes a blacklist monitoring tool that continually checks if your email address or domain has been blacklisted. By staying informed about your blacklist status, you can take immediate action to resolve any issues, ensuring your emails reach their intended recipients. 

Try Email Blacklist Checkers 

EmailListVerify offers a free tool to check if your email is on a blacklist. Services like MXToolBox and Barracuda provide comprehensive checks across multiple blacklists, helping you understand your email’s status better. Here are some other popular options to keep in mind: 

• Invaluement 

• MultiRBL 

• SpamCop 

• SpamHaus 

• SURBL

How to Get Off Email Blacklists?

Unfortunately, even if you’ve taken as many preventative measures as possible, you can still find yourself on an email blacklist. This doesn’t mean you’re a terrible emailer—these systems are imperfect and can make mistakes. The first thing to do is to request being removed from the email blacklist. Sometimes this is as easy as submitting a request to the blacklist provider; other times, you’ll have to prove to the provider that you’re a legitimate company and you’re working toward creating a better reputation for your email address.

Steps to Take for Email Blacklist Removal: Re-permission Requests and Double Opt-In Policies

Blocklist operators may ask you to complete a few tasks or implement a new protocol before removing you from the list. For instance, they could require that you send your subscribers a re-permission request that allows them to express their desire to continue receiving mail from you. Other times, the blocklist operator may ask that you create a double-opt-in subscription policy if you don’t have one.

Steps to Recover from an Email Blacklist: From Permission Pass Campaigns to Starting Fresh

Remember that being removed from a list is often on a case-by-case basis, and you may not always have control over being removed.

Run A Permission Pass Campaign

A permission pass campaign involves contacting your email list to confirm their interest in continuing to receive your emails. This step ensures your email list is engaged and compliant with anti-spam laws. 

• It’s a proactive measure to clean your list and help email deliverability.

• Segment your email list to target inactive or uncertain subscribers.

• Design a clear, concise email asking their explicit permission to continue receiving your emails.

• Include a straightforward opt-in link or button in the email.

• Send the permission pass email to the segmented list.

• Track responses and remove anyone who doesn’t opt in or actively chooses to unsubscribe.

• Update your email list to reflect only those who have confirmed their subscription.

Send A Blacklist Removal Request

To send a blacklist removal request:

• Identify which blacklist you’re on.

• Visit the blacklist’s official website to find their specific removal procedures. This typically requires filling out a delisting request form, where you’ll explain the corrective actions you’ve taken to address the issues that led to your blacklisting.

• Follow up as necessary, but remember, removal isn’t always instant and may require additional steps based on the blacklist’s policies.

Wait For The Time-Based Removal

Some blacklists automatically remove entries after a specific period if no further harmful activity is detected from the email sender. This time-based removal process can vary by blacklist, with some requiring days, weeks, or even months before delisting occurs. During this waiting period, be sure to address any issues that led to the blacklisting and avoid additional infractions.

Try Self-Service Removal (If Possible)

For self-service removal from an email blacklist, many blacklists provide a process on their website where you can request to be delisted. This typically involves verifying ownership of the email address or domain and confirming that the issues causing the listing have been resolved. For some types of blacklists like the truncate blacklist, requesting removal is not an option. In these cases, like truncate blacklist removal, you’ll need to use alternative methods.

Note: After being removed from a blacklist, it’s essential to continue best email practices to avoid future listings, such as maintaining list hygiene and monitoring for spam traps.

Start From Scratch

Unfortunately, some email accounts and domains can’t be redeemed—if you cannot remove your address from the list, you may need to start over with a new IP address. When setting up a new IP address, make sure that you take protective measures that will prevent you from ending up on the blacklists again.

Related Reading

• Microsoft Blacklist
• Remove Domain from Blacklist
• Check if Email Is on Blacklist

Start Buying Domains Now and Set Up Your Email Infrastructure Today

Inframail revolutionizes cold email infrastructure with unlimited inboxes at a single flat rate. With Microsoft-backed deliverability and dedicated IP addresses, we help scale their outreach efficiently: 

• Agencies

• Recruiters

• SDRs 

Main benefits of using our service: 

• Automated SPF, DKIM, and DMARC setup

• Dedicated email servers for each user

• 16-hour priority support daily

Gone are the days of wrestling with technical configurations and paying per inbox. With Inframail’s email infrastructure tool, you can buy domains and set up your email infrastructure today. 

Avoid Technical Headaches With Automated SPF, DKIM, and DMARC Setup

Technical configurations like SPF, DKIM, and DMARC are vital to improving your email sender reputation and avoiding the dreaded blacklists. Inframail automates these processes so you can focus on using your new email infrastructure to reach more prospects. 

Enjoy Dedicated Email Servers For Each User

With Inframail’s cold email infrastructure, users enjoy a dedicated email server. This means the actions of other users won’t impact your email deliverability. If someone else on your email service has poor sending practices or gets blacklisted, it won't affect your outreach. Enjoy peace of mind as you ramp up your cold email outreach efforts. 

Rely On 16-Hour Priority Support Daily

Inframail’s email infrastructure tool includes 16-hour daily priority support to quickly solve any issues as you scale your cold email outreach. You won't be left in the dark without help if you encounter a technical problem.