Why am I getting bot signups with domain names in the email address?
Michael Ko
Co-founder & CEO, Suped
Published 8 Jun 2025
Updated 18 Aug 2025
8 min read
It can be incredibly frustrating to see your email lists polluted with bot signups, especially when those email addresses include unusual domain names like "domains" or random character strings. This isn't just an annoyance, it also poses significant risks to your email deliverability and sender reputation. When these bots register through your forms, whether they are newsletter signups, free trial registrations, or content downloads, they can trigger a cascade of negative effects that impact your ability to reach your legitimate subscribers.
The pattern of receiving these signups in monthly or periodic batches can be particularly puzzling. It suggests automated attacks, often coordinated, rather than random, isolated incidents. Understanding the motivations behind these bot activities is the first step in effectively combating them and protecting your valuable email infrastructure.
I've seen many businesses struggle with this issue, and the impact can range from skewed analytics and increased email service provider costs to severe damage to sender reputation. Ultimately, it can lead to your legitimate emails landing in the spam folder or being rejected outright by recipient servers. It's a problem that requires proactive measures to safeguard your email program.
Why bot signups occur
Bot signups, especially those with unusual domain patterns, are not random acts of digital mischief. There are several clear motivations behind these automated attacks, all of which aim to exploit or compromise your online assets or email system.
One primary reason is to harm your sender reputation. By signing up with fake or invalid email addresses, bots cause your emails to bounce, leading to higher bounce rates. Email service providers (ESPs) and internet service providers (ISPs) monitor these metrics closely. A consistently high bounce rate signals to them that you might be sending unsolicited mail or managing a poor-quality list, which can lead to your emails being marked as spam or your sending domain (and even IP address) being added to a blacklist (or blocklist).
Another common motivation is to probe for weaknesses in your website or application. These bots often fill out forms indiscriminately, looking for any vulnerability they can exploit. This could be a precursor to more sophisticated attacks, like injecting malicious code or attempting to gain unauthorized access. Sometimes, it's also a form of black hat SEO, where bots attempt to create profiles or submit comments with spammy links, even on irrelevant forms, hoping to gain backlinks or disrupt services.
The impact on deliverability
When your email list is flooded with fake signups, it directly impacts your email deliverability. Sending emails to these non-existent or malicious addresses wastes your sending quotas and can lead to your sending domain being flagged by anti-spam systems. This means that even your legitimate emails may end up in the spam folder or be rejected. Identifying these suspicious contacts is crucial to maintaining your sender reputation.
The presence of bot-generated email addresses, especially those with odd domain names or patterns, can also lead to your domain reputation suffering. ISPs like Google and Yahoo closely monitor how well you manage your lists. A poor reputation means your emails are less likely to reach the inbox, impacting your marketing efforts and customer communication. To learn more about how to identify and prevent these types of sign-ups, you can refer to our article on how to identify and prevent spambot sign-ups.
Identifying suspicious patterns
Identifying bot signups often involves looking for specific patterns that deviate from normal user behavior and email address formats. These can be subtle, but with careful observation, you can spot them.
Look for repetitive or nonsensical patterns in the email address itself. This includes strings of random characters, common dictionary words combined with numbers, or the suspicious inclusion of keywords like "domains," "test," or "dummy.email". The username part before the @ symbol might also feature unusual combinations, or the domain itself could be a free, disposable email service or a newly registered, obscure domain. You might find more details on this in our guide on identifying bot signups and their reasons.
Beyond the email address, examine other signup data. Do the first and last names provided match the email address, or are they random characters too? Are there patterns in the IP addresses, such as multiple signups from the same IP or from known proxy/VPN services? The periodic nature of these attacks, like the monthly cadence you observed, is also a strong indicator of automated bot activity. It suggests a scheduled bot run targeting your forms.
To stop these bot signups, especially those using unusual domain names, a multi-layered approach to form protection and email list hygiene is essential. No single solution is foolproof, but combining several methods significantly reduces your vulnerability.
One of the most effective methods is implementing double opt-in. This requires new subscribers to confirm their email address by clicking a link in a confirmation email. Bots typically don't complete this step, preventing them from being added to your active list. While some marketers resist double opt-in due to a perceived slight reduction in signup rates, the quality of your list drastically improves, safeguarding your sender reputation. For more on preventing such sign-ups, consider reviewing our article on how to prevent bots from signing up.
Another crucial layer of defense involves CAPTCHAs and honeypots. Google reCAPTCHA is a widely used solution, and services like Cloudflare'sManaged Challenge offer robust bot protection. Honeypots are invisible form fields that human users won't see or fill, but bots will. If a bot fills out this hidden field, you know it's not a legitimate submission and can block it. These methods add friction for bots without significantly hindering real users. For more comprehensive insights, check out our guide on preventing bot signups on newsletter forms.
Lastly, real-time email validation and domain blocklisting can be powerful tools. Validation services check if an email address is valid, deliverable, and not a known disposable or spam trap address before it even hits your list. You can also manually or automatically blocklist (or blacklist) specific domains that frequently appear in bot signups, preventing any future registrations from those sources. This proactive approach helps maintain the cleanliness of your lists.
Before protection
High bounce rates: Email lists filled with invalid or fake addresses lead to increased hard bounces, damaging sender reputation.
Skewed analytics: Engagement metrics (open rates, click-through rates) are artificially lowered due to non-existent subscribers.
Increased costs: Paying your email service provider for sending to or storing invalid contacts.
After protection
Improved deliverability: Cleaner lists lead to higher inbox placement rates and better sender reputation.
Accurate reporting: Real engagement metrics provide clearer insights into campaign performance.
Cost savings: Reduced expenses by not sending to or storing fake email addresses.
Prevention method
Description
Impact on bots
Impact on legitimate users
Double opt-in
Requires users to confirm their email address via a link in an email.
Highly effective, as most bots won't open or click the confirmation link.
Adds a small step, may slightly reduce conversion rates for some users.
CAPTCHA
Challenges like Google reCAPTCHA or Cloudflare'sManaged Challenge to verify human users.
Effective against most automated bots, particularly those not specifically designed to bypass modern CAPTCHAs.
Minimal friction for most users, but can be a barrier for those with accessibility needs or in certain network environments.
Honeypot fields
Invisible form fields that, if filled, indicate a bot submission.
Very effective against unsophisticated bots that fill all available fields.
No impact on legitimate users, as the field is hidden from them.
Email validation
Verifies email address syntax, domain existence, and common disposable email providers in real-time.
Blocks invalid or known spam email patterns before they are added to the list.
Ensures only valid emails are added, with minimal impact on real users.
Implement strong form security
Ensure your signup forms are protected with modern security measures like reCAPTCHA (v3 or Enterprise for a seamless user experience), or a strong bot detection system. While some older CAPTCHA versions can be annoying, newer invisible ones are far less intrusive. Consider using a honeypot field, an excellent invisible defense against many bot types. Regularly review your form's security settings and logs.
Views from the trenches
Best practices
**Implement strong security:** Ensure all signup forms use modern bot prevention, such as reCAPTCHA v3 or Cloudflare's Managed Challenge, to filter automated submissions.
**Leverage double opt-in:** Always use double opt-in for new signups. This simple step confirms the email address is real and active, eliminating most bot-generated entries.
**Monitor and analyze signup data:** Regularly check your signup logs for patterns like unusual domain names, random character strings, or consistent IP addresses, which indicate bot activity.
**Utilize email validation services:** Employ a real-time email validation service at the point of signup to block invalid or disposable email addresses before they enter your list.
**Segment and clean lists:** Isolate suspicious signups into a separate segment for review, and routinely remove unengaged or bouncing addresses to maintain list hygiene.
**Track and block suspicious IPs:** Actively monitor and block IP addresses or ranges that show consistent bot activity to prevent future attacks from those sources.
Common pitfalls
**Relying solely on single opt-in:** This makes your forms highly vulnerable to bot attacks and quickly degrades list quality, leading to deliverability issues.
**Ignoring signup patterns:** Failing to analyze incoming signup data for suspicious domains or odd user information means bots can go undetected for long periods.
**Delaying list hygiene:** Not promptly removing invalid or unconfirmed contacts. Keeping them on your list increases bounce rates and sender reputation damage.
**Overlooking form vulnerabilities:** Simple forms without CAPTCHA, honeypots, or rate limiting are easy targets for automated scripts, inviting spam signups.
**Underestimating bot motivations:** Assuming bot signups are harmless. They can be part of broader attacks to damage reputation, probe systems, or generate spam.
**Avoiding necessary friction:** Resisting security measures due to concerns about slightly impacting legitimate user conversion rates, leaving your system exposed to significant risks.
Expert tips
Use a combination of visible and invisible bot prevention methods for maximum effectiveness without severely impacting user experience.
Regularly update your bot prevention tools, as bots evolve to bypass older techniques.
Beyond simply blocking, analyze the characteristics of bot signups to understand new attack vectors.
Consider rate-limiting signups from single IP addresses to prevent rapid, large-scale bot attacks.
If using WordPress, be mindful of themes and plugins that might introduce vulnerabilities, and keep them updated.
Set up alerts for unusual spikes in signups so you can react quickly to potential bot attacks.
Marketer view
If not explicitly bots, then it is certainly a form of signup abuse. Implementing CAPTCHA, honeypot, or tracking IPs at signup is recommended to identify these.
2024-02-04 - Email Geeks
Marketer view
It is likely either random griefing or a malicious actor using your form as an email validator to test email addresses.
2024-02-04 - Email Geeks
Protecting your email ecosystem
Bot signups with unusual domain names are a persistent challenge for anyone managing online forms and email lists. These automated intrusions can severely impact your email deliverability, inflate your costs, and skew your analytics, making it harder to engage with your genuine audience.
By understanding the motivations behind these attacks and diligently applying robust prevention strategies, you can protect your email ecosystem. Implementing double opt-in, utilizing advanced CAPTCHA and honeypot solutions, and performing real-time email validation are crucial steps. Regularly monitoring your signup data for suspicious patterns and promptly cleaning your lists are ongoing tasks that will ensure your email program remains healthy and effective.
Proactive email security isn't just about preventing bad data, it's about preserving the integrity of your sender reputation and maximizing your inbox placement. By taking these steps, you safeguard your ability to connect with your valuable subscribers, ensuring your messages reach their intended destination.
Google and Yahoo closely monitor how well you manage your lists. A poor reputation means your emails are less likely to reach the inbox, impacting your marketing efforts and customer communication. To learn more about how to identify and prevent these types of sign-ups, you can refer to our article on how to identify and prevent spambot sign-ups.
Cloudflare'sManaged Challenge offer robust bot protection. Honeypots are invisible form fields that human users won't see or fill, but bots will. If a bot fills out this hidden field, you know it's not a legitimate submission and can block it. These methods add friction for bots without significantly hindering real users. For more comprehensive insights, check out our guide on preventing bot signups on newsletter forms.
