The Complete Guide to Preventing Spam Signups and Protecting Your Email List

This guide equips you with all the spam prevention and removal techniques you need to keep your email list sparkling clean. Extinguish fake signups, engage real subscribers, and watch your email marketing thrive.

What are Spam Signups and Why are They Harmful?

Seeing a sudden spike in new subscribers may seem like cause for celebration at first. But before you break out the champagne, it’s important to determine—are these real people excited to hear from you? Or spam signups?

Unfortunately, the latter is a common occurrence, and left unchecked can wreak havoc on your marketing efforts. In this section, we’ll cover what exactly spam signups are, why they are harmful, and how to identify them.

What is a Spambot?

A “spambot” is a type of malicious software program designed to automatically fill out online forms with fake or stolen data. Their primary purpose is to infiltrate email lists, comment sections, and other targets in order to spread spam or malware.

Spambots are programmed to scour the internet searching for any site that allows visitors to submit their email address or other information through a signup form or field. Once found, they can generate and enter in fake credentials at lightning speed.

Some common characteristics of spambots:

  • Operate 24/7 and submit thousands of signups per day
  • Typically have no human oversight or control
  • Use algorithms to generate fake emails and names
  • Can detect “honeypot” fields meant to stop bots
  • Continuously evolve to evade new bot detection methods

In short: spambots are robotic nuisances that submit deceptive signups to steal resources and undermine digital operations.

How Spambots Attack Your Forms

Spambots pursue two major objectives when bombarding your signup forms:

1. Spreading spam and malware

After gaining access to your email list, spambots can use it as a vehicle to spread junk email containing links to phishing sites, malware downloads or other malicious content.

Even if only a small percentage of your list falls for a spam email attack, that can still cause significant damage through compromised accounts, identity theft, and infected devices.

2. Sabotaging deliverability

By filling your list with invalid, unengaged addresses, spambots drag down key email metrics like open and click rates. This signals to ISPs that your emails are unwanted, leading to increased spam folder filtering.

Low engagement caused by fake signups becomes a self-fulfilling prophecy, as fewer real subscribers interact with your emails due to never seeing them in the first place.

Dangers of Fake Signups

Allowing spam signups to infiltrate your email list can negatively impact your marketing and communications in the following ways:

Damaged Sender Reputation

Too many bounces and spam complaints tied to a sender domain can cause ISPs like Gmail to assign a poor “sender score.” This results in emails increasingly tagged as spam or rejected entirely.

According to 250ok, just 100 spam complaints can cause senders to be blacklisted by major ISPs. Fake signups generate unnecessary complaints.

Wasted Resources

Storing and managing fake signups takes up storage space and computing resources. Marketing teams also waste time and effort creating content for an inflated, disingenuous audience.

The more data and decisions driven by spammy lists, the further you get from reaching and engaging real subscribers.

Inaccurate Metrics

With bot signups mixed into your reports, all key metrics like open rate, click rate, and unsubscribe rate become unreliable.

This distorts your analysis, as poor engagement is wrongly attributed to content and messaging rather than fake subscribers.

Increased Risk of Fraud

In addition to spreading malware, compromised lists can be exploited for phishing, sending fraudulent links or messages to customers. Brand reputation and trust can take a big hit.

Fake accounts with valid emails also steal free trials, coupons and other resources intended for real leads and customers.

The takeaway? Like an infected wound, fake signups will only become more harmful if left untreated. The rest of this guide covers how to diagnose, treat and prevent spam subscribers.

How to Identify Spam Signup Attacks

Like viral infections, spam attacks come in all shapes and sizes. From small infiltrations to widespread outbreaks, it’s essential to quickly diagnose an attack. The sooner you can confirm and assess the problem, the quicker you can treat it.

This section covers the most common signs of a spam attack, as well as tools to help expose sneaky fake signups.

Warning Signs of a Spam Attack

Here are some key indicators that spam bots have your signup forms in their crosshairs:

Sudden Influx of Signups

A spike in signups over a short period of time, such as getting 1,000+ new subscribers in an hour, is a strong signal of bots at work. Even a spike over a few days could indicate a problem.

Of course, a surge in signups isn’t always bad. Promotional campaigns and viral content can also rapidly grow your audience. But it’s worth investigating closely if acceleration seems abnormal.

Similar/Identical Signups

Spam bots generate signups using templates and algorithms. Rather than unique individuals, you may see:

Grouping and sorting signups can help uncover suspicious patterns like these.

Disposable Email Addresses

Services like Mail Musk, Temp Mail or 10 Minute Mail offer temporary, anonymous inboxes often tied to fake signups.

Temp email addresses typically have domains like:


Unusual Geography

If signups suddenly pour in from a single foreign country that’s normally unassociated with your business, bots could be to blame.

For example, a UK-focused newsletter getting 1,000 Brazilian subscribers overnight likely indicates fake signups. Check the location data of new signups for anomalies.

Fake Information in Fields

Lastly, bad data itself can confirm bots. Submissions with:

  • Gibberish names: “Asdfsdf Kjhkjh”
  • Fake domains: [email protected]
  • Junk addresses: 123 Main Street, Schenectady NY 12345

are clearly spam. Review form submissions for nonsense and false data.

Tools to Detect Fake Signups

Relying on just manual monitoring and eyesight to catch spam attacks has its limits. Several tools exist to automatically sniff out fake signups:

Email Verification Services

Tools like ZeroBounce and Mailgun verify the validity of email addresses down to the syntax, domain, and mailbox. Just plug in your list to identify bad emails.

List Cleaning Software

MailerLite’s own verification tool as well as apps like EmailListVerify will scrub your list for fake signups and inactive emails.

Analytics to Spot Trends

Reviewing signup and campaign analytics regularly can reveal odd engagement patterns, especially when compared to historical performance.

For example, monitoring social traffic sources can show if an unusual platform is funneling tons of signups, indicating a possible spam source.

Catching fake signups quickly is critical to keeping your email program healthy. With the right knowledge and tools, identifying spam attacks doesn’t have to be a complex or lengthy process.

Implementing preventative measures covered later is still the best medicine though. Just like with viruses, an ounce of prevention is worth a pound of cure when it comes to spam subscriber outbreaks.

Knowing Your Audience

Preventing Spam Signups on Your Forms

Now that you know how dangerous fake signups can be, let’s get to the good stuff—prevention.

Blocking spam bots and keeping your forms pristine requires combining both “active” and “passive” measures.

Think of it like home security:

  • Passive measures like alarm systems and locks make your home undesirable and difficult to enter.
  • Active measures like surveillance cameras and guards alert you to intruders and allow quick responses.

Similarly, you need preventative barriers to repel and discourage spam bots. But also ongoing monitoring to detect any that make it through.

Here are some of the most effective techniques and tools to guard your signup forms:


CAPTCHAs or reCAPTCHAs are the most direct ways to restrict bot signups by distinguishing real humans from automated scripts.

Traditional CAPTCHAs require users to decipher and input hidden letters or numbers. But thanks to machine learning advancements, many CAPTCHAs have now become ineffective against advanced bots.

That’s why today’s go-to solution is Google’s reCAPTCHA v2 and v3.

reCAPTCHA analyzes many behavioral signals—from mouse movements to device tilt—to determine if users seem human. After checking the box, subtle verification continues in the background.

Benefits of reCAPTCHA:

  • Easy UX – single checkbox vs confusing characters
  • AI-powered bot detection
  • Low false positive rate – won’t block real users
  • Seamlessly integrates with most forms
  • Free to use

Get started adding reCAPTCHA using the official reCAPTCHA developer docs.

Enable Double Opt-In

Double opt-in adds an extra verification step before subscribers are added to your list. It works like this:

  1. Visitor signs up by submitting their email address
  2. You send a confirmation email to that address
  3. Visitor must click the link inside that confirmation email

Only after completing step #3 will the signup be considered valid. This prevents bots accessing inboxes from finalizing fake subscriptions.

Benefits of double opt-in:

  • Verifies real, accessible email addresses
  • Engages subscribers from the start
  • Gives clear consent to receive emails
  • Easy to set up in most email services

The downside is adding a hurdle before subscribers are added. Make sure your confirmation email clearly communicates the value subscribers gain by verifying. Many businesses offer instant free content downloads after confirming to incentivize completing this extra step.

For implementation details, see Mailchimp’s guide on double opt-in.

Add Honeypot Fields

Honeypots are the venus flytraps of form spam prevention. They look like normal form fields but don’t actually submit any data.

For example, you could add a hidden “Company” text field labeled “Leave this field empty”:

<label class="visuallyhidden" for="company">
  Leave this field empty 

<input id="company" name="company" type="text"> 

The field is invisible to humans but bots will detect it and dutifully fill it in. You can then automatically filter out any submission containing data in your honeypot.

Other types of honeypot fields:

  • Hidden “Terms of Service” checkbox – checked = bot
  • Select menu with no visible options – any option selection = bot
  • Empty text field labeled “Do not fill” – any text input = bot

Honeypots are simple yet effective against less sophisticated bots. However, some smart bots may detect and avoid them, so don’t rely on honeypots alone. Use them as one layer of defense.

Implement Email List Verification

Rather than playing endless games of cat and mouse with sneaky bots, you can shift to offense by verifying the quality of your list after signups occur.

List verification services like ZeroBounce will analyze all your subscriber emails for:

  • Syntax accuracy – [email protected]
  • Valid domain –
  • Catch-all patterns – [email protected]
  • Disposable/temporary emails
  • Bounce back traps – name@[yourdomain].com

After scanning, you receive a report of all high-risk and invalid emails to segment out. This audit ensures your list stays clean despite any bots that evade initial protections.

Most verification services offer a free trial so you can test list coverage before fully investing.

Block Known Spam Domains and IPs

When you spot a clear pattern of spam signups from a shady domain name, URL or IP address, fight back by blocking traffic from those sources completely.

Common tactics include:

Blocking domains in sign up forms – Many form builders allow restricting certain domains like from submitting your forms.

Blacklisting IPs in server configs – Web hosting access allows adding malicious IPs to an application blacklist. Requests from blacklisted IPs are blocked.

Email filtering rules – Email services can apply filters that delete or reject messages sent from flagged email addresses and IPs.

Rate limiting – Limiting how many form submissions or emails can come from the same source makes automation more difficult.

CAPTCHAs triggered by suspicious activity – Rather than putting CAPTCHAs on every form, you can selectively activate them after detecting spam signals like unusual submission rates. This avoids over-burdening legitimate users.

The more channels you can choke off, the less rewarding and effective fake signups become for attackers.

Use Two-Factor Authentication

For accounts and pages allowing visitors to create profiles or access gated content, adding two-factor authentication (2FA) provides stronger identity verification.

2FA typically combines:

  • Something you know – password, PIN
  • Something you have – SMS code, hardware token

So users might enter their password (knowledge factor) then get a code texted to their phone (ownership factor) to complete logging in.

Because bots lack phones to receive SMS codes (for now!), 2FA blocks them from creating accounts for spam purposes under the guise of real people.

Popular 2FA options:

  • SMS codes – Simple and accessible to most people
  • Authenticator apps – Like Google Authenticator or Authy
  • USB keys – Physical tokens that plug into devices
  • Biometrics – Fingerprint, face, or iris scanning

Start by enabling 2FA for any administrator, editor and other privileged accounts that could cause major damage if compromised. Then expand user coverage from there.

Keep Software Updated

Here’s a precaution that takes just a few minutes but delivers big security benefits.

Ensure any software related to your signup forms and email campaigns—the CMS, form plugins, email service, etc.—are all fully updated.

Maintaining current versions reduces your vulnerability to:

  • Known exploits – Updates patch holes that bots leverage to sneak onto lists.
  • Spam app vulnerabilities – Plugins with security flaws become backdoors. Keep them updated.
  • Enhanced bot defenses – Updates often improve algorithms and rules against new spam tactics.

Don’t stop at major versions either. Enable auto-updates to add security patches as soon as they become available. This denies attackers opportunities to capitalize on known weaknesses.

Treat software updates as routinely as changing air filters or topping off wiper fluid. Just basic maintenance required to keep your online business vehicle cruising safely.

Monitor Signup Activity and Data

Passive prevention and active monitoring combine to offer comprehensive spam defense.

Your defenses should generate signals allowing you to confirm an attack is happening and respond appropriately.

Examples of analytics providing valuable threat intelligence:

  • Traffic spikes – Unexpected surges in signups
  • Bounce rates – Growing hard/soft bounce rates
  • Unsubscribe requests – More unsubscribes, especially from new signups
  • Open/click rates – Lower engagement from recent subscriber cohorts
  • Spam button clicks – Increasing spam complaints or blocked opens

Driving decisions with data allows you to optimize defenses over time and catch attacks that slip through the cracks.

Aim to make fake signups an exercise in frustration causing nothing but wasted effort for attackers. Combining multiple layers of passive blocking and active monitoring creates a formidable anti-spam fortress.

Removing Spam Signups from Your Email List

Like weeding a garden, keeping the pests and weeds (spam) cleared from your email list is an ongoing task.

Even with protections in place, some amount of junk will make it through. Whether from sophisticated bots evading defenses or false positives in your filtering, expect to regularly purge bad signups.

Here are tips for efficiently pruning fake emails from your list.

Use Segmentation to Filter Spam Contacts

Segmenting allows dividing your contacts into groups based on shared traits—like sign up source, location, or engagement. This makes targeting and filtering much easier.

Create segments to isolate spam signups using criteria like:

  • Email domain (filters addresses)
  • Date added (filters signups after a spam attack)
  • Weird names (filters gibberish names)

Build segments with:

  • Your email service segments – Most ESPs like Mailchimp allow segmenting contacts.
  • Custom code – For advanced segmentation logic when needed.
  • External segmentation software – Tools like Mailshake offer robust segmentation.

Regularly run your spam-filtered segments and mass delete or unsubscribe those contacts to keep cleaning your list.

Manually Review and Remove Suspicious Emails

Even with automation, human oversight is still needed to catch sophisticated spam and prevent mistakenly losing real subscribers.

Factor in these manual email list hygiene practices:

  • Sort by email domains – Scan domains for suspicious patterns like sequential numbers.
  • Review recent signups – Check any unusual activity periods for fake emails.
  • Check low engagement groups – Inactive users more likely to be invalid signups.
  • Cross-reference key metrics – Compare opens, clicks, bounces, etc to flag outliers.

Build a routine for periodically inspecting and tidying up your list. Monthly or quarterly deep dives ensure you don’t miss spam buildup between automated sweeps.

Pro Tip: Take screenshots of metrics before cleaning your list. This allows comparing metrics afterwards to confirm your efforts paid off through increases in open rates, lower bounce rates, etc.

Regularly Clean Your Email List

List cleaning should be an ingrained habit, not just a reaction to spam attacks. Set a schedule for thoroughly inspecting and optimizing your data.

A comprehensive list cleanse includes:

  • Removing clearly invalid emails
  • Verifying suspect or inactive emails
  • Deleting unengaged contacts
  • Updating changed subscriber profiles
  • Merging duplicate records

Think of spring cleaning. You:

  • Clear out junk buildup
  • Deep clean every corner
  • Fix anything broken
  • Organize and optimize

Your email list needs the same seasonal refreshes!

Batch cleaning tools like MailerLite’s Verifier make the process fast. But for ultimate peace of mind, a manual verification pass is still recommended.

Set reminders to clean your email garden regularly, and you’ll enjoy more email success with fewer pesky spam weeds.

Maintaining a Healthy Email List Free of Spam

Congratulations, you now have all the necessary tools to transform your list from a spam-ridden swamp to a pristine subscriber oasis! But the work doesn’t stop once your defenses are in place.

Maintaining your email hygiene requires ongoing refinement and vigilance. This final section covers core strategies for keeping your list lean, clean and spam-free.

Importance of Quality Over Quantity

One mindset shift that helps immensely is prioritizing email list quality over quantity. It’s better to have 1,000 engaged subscribers than 100,000 vague contacts.

Focus on:

  • Relevance – Subscribers genuinely interested in your content
  • Intent – Signing up to learn, purchase or support you
  • Engagement – Clicking, sharing, replying to emails
  • Satisfaction – Unsubscribes remain low

Large yet unreliable lists packed with spam decay deliverability. Smaller high-quality lists foster connection with your real supporters.

As you strengthen defenses, expect your list growth to slow while engagement improves. This tradeoff means your efforts are working!

Ongoing Monitoring and Refining

Complacency is the first step towards another outbreak. You must continually:

  • Review metrics – Watch for anomalies indicating spam surges
  • Tune defenses – Improve weak points and detection rules
  • Update software – Maintain the latest security patches
  • Verify subscribers – Periodically re-check old and new signups

Make list health monitoring a recurring task on your calendar, not a one-off project.

Pro Tip: Designate a spam-fighting point person on your team to own oversight and be responsible for rallying resources when attacks strike.

Balance Incentives and Verification

As mentioned earlier, limited-time discounts and free trials—while great for conversion—also attract spammers.

When boosting signups with special offers:

  • Cap claims – Limit 1 per customer or household
  • Add friction – Require making an account first
  • Obscure details – Provide codes only after email verification
  • Confirm humanity – Use CAPTCHA and 2-factor authentication

You want to minimize opportunities for exploitation while staying friendly to real users.

For example, require an email confirmation before revealing a coupon code. Good subscribers won’t mind an extra step for extra savings.

To maintain an orderly garden, you must regularly nurture desired growth while eliminating unwanted weeds. Keeping your email ecosystem in balance takes commitment, but pays off through a thriving list.

Stay vigilant, stick to list cleaning routines, and let your hard work cultivating engaged subscribers bloom.

Summary: Preventing Spam Signups to Keep Your Email List Healthy

  • Fake signups from spam bots can seriously harm email sender reputation, deliverability, and engagement. Be vigilant in keeping them away.
  • Use tools like reCAPTCHA and double opt-in to add friction during signup and prevent bots. Email list verification services can clean existing lists.
  • Watch for signals like unusual signup spikes, odd email domains, and low engagement as indicators of a spam attack.
  • Blocking known spam sources, enabling two-factor authentication, and keeping software updated strengthens your defenses.
  • Segment out spam subscribers and manually review lists periodically to purge bad emails. Ongoing monitoring and hygiene is crucial.
  • Prioritize list quality over quantity. Incentives like coupons should be paired with protections like CAPTCHA to minimize exploitation.
  • A multilayered defense combining prevention, detection and removal is needed to maintain a healthy, growing email list free of spam.

Frequently Asked Questions

Q: How can I tell if a spike in signups is real or spam?

Look at factors like the email domains, signup source, geography, and other traits of the new subscribers. If lots of emails are from temporary domains, the same IP, foreign countries unrelated to your business, etc. then it’s likely spam.

Q: Are honeypots detectable by advanced bots?

Some sophisticated bots may recognize common honeypot patterns. But many will still get tricked. Honeypots are one layer of defense and should be used in addition to other measures like reCAPTCHA and email verification.

Q: Should I make my signup form as minimal as possible?

Collecting just an email address does make it easiest for visitors to convert. But also easiest for bots! Collect additional data like name, company, location etc. to verify humanity without overburdening subscribers.

Q: How often should I purge my list of spam?

Ideally, inspect your email list weekly or monthly and remove any suspicious signups. Quarterly or biannual “deep cleans” are also recommended to catch issues building up over longer periods. Make cleaning recurring maintenance for list health.

Q: Can spam attacks get my emails flagged as spam?

Yes – fake signups hurt your sender reputation and engagement metrics, causing providers to see your emails as unwanted. This leads to more emails sent to spam folders. Minimizing spam signups helps maintain inbox delivery.

Q: Should I use an email confirmation and CAPTCHA on the same form?

Absolutely! The two complement each other well. CAPTCHA blocks bots upfront, then confirmation verifies subscribers are real people with accessible inboxes. Using both provides layered protection.

Q: How do spammers get real email addresses to sign up with?

Attacks, breaches, and scraped web data give spammers real addresses. Always assume some portion of signups, even with valid emails, will be spam. Verification and active monitoring is still essential with existing inboxes.