This is a guest Post written by email industry expert Leon Hoppe
Lately, I have been getting a lot of questions about non-human interactions AKA bot clicks in email lists. Which has been causing significantly inflated open rates and click rates.
It’s a fair question and one that deserves some clarity.
Let’s take a step back.
A Brief History of Open Rates.
Historically, the open rate has never been a perfect signal of engagement. But there was a time when it felt reliable. We based a lot of our segmentation on this metric.
Back When Opened Meant Interested.
That’s because, years ago (showing my career age, and yes, I found the fountain of email youth), tracking an open usually relied on someone taking action like clicking “view images” in their inbox. If images didn’t load automatically, an open required curiosity or intent, or a click on a call to action.
Marketers leaned on this signal. It wasn’t perfect, but it gave them a directional gauge: “Did someone want this email?”
Most were casting the widest net possible and hoping a big open or click number would yield results.
But… the ecosystem evolved.
Now that we have the brief history lesson. Let’s move on.
What’s a Non-Human Interaction (AKA Bot) Anyway?
When I talk about “bots” in email, I’m referring to things like automated opens or clicks that don’t come directly from a person.
These are actions triggered by systems, privacy features, security tools, spam filters, or mailbox providers that scan or pre-load parts of your email (like images or links) before the recipient ever sees it.
For the most part, these actions are designed to protect users. Non-consumer mailboxes on custom or institutional domains: corporate domains like @acme.com, and institutional domains like .org, .gov, .mil, .edu, and K-12 patterns (e.g., @district.k12.state.us`) are quietly opening and clicking, making traditional marketing metrics feel a little messy.
What Good Metrics Often Looks Like (Not a Rulebook)
In many B2C programs, a healthy list roughly resembles 40–60% Gmail, 20–30% Yahoo family, 5–10% Microsoft, 2–5% Apple, with the rest scattered across smaller providers.
It varies by niche, so treat this as a temperature check, not a rule. The trend to watch is business/institutional email addresses creeping upward. When that happens, bot noise tends to rise and revenue per send tends to fall.
As a general guardrail, keeping business/institutional around 10% or less, ideally closer to 5%, keeps analytics honest.
But How Do I Know If I Have a Problem?
Many teams still define “engaged” as “opened or clicked in the last X days.” As the business address share grows, those segments turn bot-heavy. The list looks healthy, but in reality, the quality of the list diminishes.
If you Have Excessive Open Rates and or Click-Through Rate.
If your reports say engagement is booming but sales are flat, you’re probably staring at a bot problem.
As your list ages and acquisition widens, more of these addresses slip in. The numbers look better; the revenue doesn’t.
That’s exactly where security layers sit, and those layers love to “engage” on behalf of users: fetching pixels, following links, scanning destinations. Nothing dramatic happens in a single send. It’s a slow tilt. Twelve months later, your email program is upside down.
To keep your decisions grounded, watch the mix. Track consumer vs. business share monthly, and look at every KPI through that lens. Do you have an extremely high open rate or click-through rate on a particular creative? Investigate by mailbox provider, is it coming mostly from tier 1 mailboxes, or bots?
Reasons For Having More Business Addresses in Your List.
1. Ineffective List Acquisition Strategies
Purchased Lists
Buying third-party email lists almost always means inheriting a pile of generic, outdated, or irrelevant business addresses that never opted in. I see this constantly. Companies fixate on the total number of emails they’re buying and completely ignore the mailbox provider mix, Gmail, Yahoo, Microsoft, corporate domains, and everything in between. They assume all inboxes behave the same and generate revenue the same way. They don’t. A list heavy in corporate domains behaves nothing like a true B2C list, especially when it comes to filtering, bots, and false engagement.
Scraped Data
Scraping emails from company websites or platforms like LinkedIn usually pulls role-based or abandoned addresses. In today’s market, job tenure is short. People move companies, teams, and roles constantly, especially over the last few years. That means scraped business emails are often already dead, reassigned, or heavily monitored by security systems before you ever send your first campaign.
Aggressive Lead Magnets Without Validation
Offering high-value content in exchange for an email address without proper validation invites low-quality data into your system. Users will often submit a work email simply because it’s convenient, not because they want marketing there. Ask yourself honestly: when you follow a personal brand or download content, are you using your company inbox or your personal one? Your audience behaves the same way, and that disconnect shows up later.
Anonymous Traffic Identification Services
Anonymous visitor identification tools attempt to reveal who’s browsing your site without filling out a form. They work by matching tracking pixels, cookies, device IDs, and hashed emails against massive third-party databases to surface details like names, email addresses, and LinkedIn profiles. When done correctly, these tools can add value in retargeting or enrichment. When abused, they shortcut consent entirely and inject unverified, bot-heavy, or corporate emails straight into automated outreach, creating serious downstream deliverability problems.
2. Lack of List Hygiene and Maintenance
Clean Data Is Non-Negotiable for Deliverability
A clean list is the foundation of inbox placement. In B2C email marketing, your subscribers should be real people using personal inboxes, not corporate addresses protected by aggressive, bot-driven security layers. Once business emails dominate your list, you’re no longer optimizing for humans; you’re optimizing against filters.
No Regular Cleaning
Email lists naturally decay. According to a 2025 study by Zerobounce, lists degrade by roughly 28% per year as people change jobs, switch roles, or abandon addresses altogether. Holding onto business emails doesn’t just mean outdated data it means keeping addresses that are often quickly deactivated or reassigned. Without consistent cleaning, these dead accounts pile up, and your campaigns increasingly interact with security bots instead of people.
Hard Bounces and Reputation Damage
Failing to immediately suppress hard bounces is one of the fastest ways to damage sender reputation. With professional domains, a single policy change or employee termination can instantly turn a previously valid address into a hard bounce. Continuing to send to those addresses signals poor list management.
Traffic Source Quality Can Supercharge the Problem.
Acquisition isn’t neutral. Strong creative and targeting on TikTok, Facebook, or YouTube often nets higher intent than quizzes, polls, purchasing lists, or low-intent arbitrage. Anonymous visitor software has been popular in the past few years, which can add scale, but comes with some risk.
Measure sources by what they add to revenue and by how they reshape your domain mix, not just by how many emails they generate.
What Can I Do to Prevent or Slow It Down?
You can take a few different approaches. Purge or contain. It’s up to you to decide.
1. Strict Purge
I prefer this option. Suppress most business and institutional domains. This is NOT a 1-time swoop. Depending on your list size, download an active domain report. Using Chat GPT Prompt:
“Generate a Non-Mailbox Domain Blocklist. When I upload an email list, identify all email addresses that do not belong to a consumer mailbox or ISP-hosted inboxes.”
From the results, classify and extract every business, brand, organization, school, government, nonprofit, or custom-hosted email domain. These are domains that are privately managed or institutionally hosted and are not mailbox providers such as Gmail, Yahoo, Microsoft, or major ISPs.
Process the list by:
Extracting the domain from each email address.
Normalizing each to its root domain.
Excluding known mailbox and ISP domains (e.g., Gmail, Yahoo, Outlook, AOL, AT&T, Comcast, Spectrum, Verizon, and similar providers).
Retaining only non-mailbox domains.
Deduplicating results so each root domain appears once.
Deliver the results as a downloadable CSV containing:
Unique root domains suitable for blocking.
Include a short summary with:
Total emails analyzed.
Total non-mailbox domains identified.
Total mailbox/ISP domains excluded.
After this is complete. You will still need to manually go through and ensure no mailbox or service provider is in the list.
Do this monthly or semi-monthly, depending on incoming volume. You’ll also lose a small amount of real revenue from the minority who insist on using work email. But you’ll snap your metrics back to reality fast and simplify reporting.
2. Staged Containment
Keep business/institutional addresses, but quarantine them in a separate stream. This can be more challenging when segmenting based on your ESP capabilities and requires having full knowledge of many of the smaller mailbox providers out there, such as charter.net, suddenlink.com, prodigy.net, hughes.net, .rr.com, etc. Send Lower frequency drops to this segment. Require some human action. For example, ask them to reply to your email. If they do, they enter a raffle. Another strategy is add in your email header that has a clickable action back to your website or a safe sender link. Then pull a report on who is clicking on those header links. You will be surprised by how many bots you catch.
Pick the model that fits your list size, resources, and performance risk tolerance. Many teams start with containment and then selectively purge the noisiest root domains once the data is clear.
A Short, Practical Checklist
1. Define your buckets: consumer webmail vs. business/institutional (corporate + .org/.gov/.mil/.edu/K-12).
2. Baseline the mix and show every KPI by bucket. Keep an eye on the trend line.
3 . Purge or stage a separate business/institutional stream with tighter rules and promotion gates.
4. Judge acquisition by revenue and domain mix, not just lead volume.
5 .Review weekly, monthly, or quarterly based on traffic volume.
The goal isn’t zero business addresses. This helps quarantine the noise so you can make better decisions.
About the Author:
Leon Hoppe has spent nearly 20 years in digital marketing, running traffic, managing affiliates, and email programs from the inside out. He started on the media buying side, scaled affiliate partnerships, and eventually became the go-to guy for fixing email systems.
He has helped marketers and publishers rebuild their email infrastructure, set up advanced tracking, and get back into the inbox.
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