Why do spambots submit real emails to signup forms?

Key findings

• Misinterpretation: Some spambots are unsophisticated, treating any input field (including signup forms) like a comment section, with the intent to inject spam links.
• Subscription bombing: Malicious actors use bots to flood email addresses with sign-up confirmations, aiming to overwhelm recipients' inboxes.
• Harassment: This can be a form of harassment against the email recipient, rendering their inbox unusable.
• Cover-up: Subscription bombing can also serve as a smokescreen, generating a large volume of legitimate-looking email traffic to hide more serious criminal actions like phishing or credential stuffing.
• Reputation damage: These actions lead to higher bounce rates and increased spam complaints for the legitimate sender, which negatively impacts their sender reputation and deliverability.

Key considerations

• Implement CAPTCHA: Utilize services like reCAPTCHA or similar challenges to effectively distinguish between human users and automated bots submitting forms.
• Use honeypot fields: Add hidden fields to your forms that are invisible to human users but detectable by bots. Any submission that fills these fields can be flagged as spam, as explained in our guide on how to protect email list signup forms from bots.
• Employ double opt-in: Always use a double opt-in process for new subscribers to confirm their intent, which is a critical step in preventing unwanted subscriptions and maintaining list quality. This is also a key recommendation for email validation best practices.
• Email validation: Implement real-time email validation at the point of entry to filter out invalid or suspicious email addresses before they even reach your list.
• Monitoring: Regularly monitor your subscriber lists for unusual activity or sudden spikes in sign-ups, which can indicate a bot attack.
• Form security: Ensure your signup forms are securely coded and protected against common bot attack vectors. Mailchimp's About Fake Signups page offers more insights into basic bot behavior.

Key opinions

• Competitive sabotage: Some marketers speculate that competitors might orchestrate these attacks to undermine their email marketing campaigns and damage their sender reputation.
• General malice: A prevalent view among marketers is that spambots operate primarily to create problems for businesses and individuals, deriving satisfaction from the disruption they cause.
• Unintended consequences: Marketers frequently report a surge in unsubscribes and spam complaints from recipients whose emails were added to lists without their explicit consent, directly impacting list engagement.
• Focus on mitigation: The primary concern for marketers is not necessarily understanding the exact 'why', but rather implementing effective strategies to stop the bot activity and protect their list health and email deliverability.

Key considerations

• List hygiene: Marketers recognize the critical need to aggressively clean their lists of unengaged or unknown users to lessen the adverse effects of bot sign-ups, as outlined in our advice on how to prevent fake email registrations.
• Bounce rates: Elevated hard bounce rates stemming from fake sign-ups are a key indicator of bot activity and demand immediate intervention to safeguard sender reputation.
• Subscriber quality: The priority for marketers remains acquiring genuinely interested subscribers, making robust anti-bot measures indispensable for maintaining high list quality.
• Deliverability impact: Marketers are acutely aware that spambot activity can directly result in emails being directed to the spam folder, significantly hindering campaign performance. This emphasizes the need to frequently determine if marketing emails are going to spam. SMTP.com offers insights into protecting sign-up forms from spambots.

Key opinions

• SEO spam bots: Experts identify unsophisticated SEO spam bots that misinterpret signup forms as comment sections, aiming to inject spam links and improve search rankings.
• Subscription bombing: This is a more deliberate and severe attack where criminals use mass sign-ups to flood mailboxes with confirmation emails, rendering them unusable for the legitimate recipient.
• Harassment tactic: One primary gain for criminals is harassing the email recipient by making their inbox unusable with a deluge of unwanted subscription emails.
• Cover for other crimes: Subscription bombing can also serve as a smokescreen, generating significant email traffic to hide phishing attacks, credential stuffing, or other malicious activities against the targeted email address.
• Disruptive intent: The core motive behind many such attacks is pure disruption, aiming to negatively impact the sender's email deliverability and the recipient's overall email experience.

Key considerations

• Preventative measures: Experts emphasize the importance of implementing effective anti-bot measures on all web forms to prevent malicious submissions from impacting email lists.
• Double opt-in as defense: Confirming subscriptions with a double opt-in process is crucial for preventing subscription bombing from affecting your active email list, even if spam traps might still be hit.
• Monitoring abuse reports: Regularly checking abuse reports and feedback loops can help identify and mitigate the impact of bot activity, preventing further damage to your email program.
• Impact on sender reputation: Experts caution that high volumes of spam complaints and bounces resulting from bot sign-ups can severely damage sender reputation and lead to blocklisting. Understanding spam traps and how they work is key. Word to the Wise offers additional insights on subscription bombing and abuse prevention.

Key findings

• Automated submissions: Documentation confirms that spambots are automated programs meticulously designed to locate and submit data to online forms, often at high volume.
• Form abuse: This behavior is broadly classified as form abuse or unwanted spam submissions, irrespective of the validity of the email addresses used.
• Variety of motives: Official sources detail motives ranging from simple link injection for SEO spam to overwhelming recipients' inboxes via subscription bombing, or even masking other nefarious activities.
• Impact on reputation: These actions severely compromise the reputation of the sending domain and IP address, frequently resulting in blocklisting and significant email delivery failures.
• Data contamination: Form spam contaminates legitimate user data with fake entries, making accurate list management and segmentation challenging for marketers.

Key considerations

• Technical defenses: Documentation consistently advocates for implementing technical measures such as CAPTCHAs, honeypots, and advanced bot detection algorithms to secure web forms. These help prevent your domain from being placed on an email blacklist.
• Email validation: Utilizing server-side email validation and verification at the point of entry is crucial for rejecting invalid or suspicious email addresses before they enter your system.
• Double opt-in mandate: For subscription forms, double opt-in is a widely recommended best practice to confirm user intent and prevent unauthorized additions to email lists, thus improving list quality.
• Monitoring and analysis: Regularly analyzing form submission data and email engagement metrics can help identify patterns of bot activity and inform proactive defense strategies, essential for improving deliverability in 2025.
• Security updates: Keeping website platforms and plugins updated is vital, as vulnerabilities can be exploited by spambots to gain access or submit unwanted data. SendLayer provides insights on how to stop contact form spam.