Why do email security filters auto-click links and run JavaScript?

Email security filters, especially those from major providers like Microsoft , are designed to proactively scan links for malicious content, including malware and phishing. They often use headless browsers or virtual environments that can render web pages and execute JavaScript, mimicking user behavior to detect dynamic threats.

What is the impact of these auto-clicks on my email marketing?

This can inflate your email engagement metrics, leading to inaccurate open and click-through rates. More critically, for opt-in emails, it can result in unintended subscriptions by bots or security scanners, potentially adding invalid or low-quality addresses to your list, which can harm your overall sender reputation .

How can I prevent security filters from auto-confirming opt-ins?

The primary solution is to remove JavaScript that automatically submits forms or redirects pages upon load. Instead, require an explicit user action, such as clicking a submit button, to confirm the opt-in. This ensures that only human interaction leads to subscription confirmation. This also helps you minimize bot clicks .

Can I distinguish between real user clicks and automated clicks?

While it's challenging to completely filter out every bot click, you can monitor your logs for unusual IP addresses or user agents, especially those associated with known security scanners . Some email service providers also offer advanced analytics that help differentiate between human and automated clicks.

Why are email security filters auto-clicking links in opt-in emails with Javascript and how can I prevent it? - Technical - Email deliverability - Knowledge base

Email security filters are a double-edged sword for marketers. While essential for protecting inboxes from malicious content, their increasingly sophisticated mechanisms can sometimes interfere with legitimate email marketing practices. A common and frustrating issue I've encountered, particularly with opt-in emails, is security filters automatically clicking links and even executing JavaScript. This behavior can lead to skewed analytics and, in the worst cases, unintended subscription confirmations.

The core problem arises when a system, such as

Microsoft's email infrastructure, preemptively scans email content. This includes following any links embedded in the email to check for potential threats like malware, phishing attempts, or spam. When these filters encounter a landing page with JavaScript that automatically triggers an action, such as submitting a form for a double opt-in confirmation, they can inadvertently complete that action without actual user interaction. This can cause significant headaches for list management and deliverability professionals trying to accurately gauge engagement and maintain clean subscriber lists.

Understanding security filter behavior

Security filters, often employing headless browsers or virtual environments, are designed to emulate a real user's experience to uncover hidden or dynamically loaded malicious content. This means they don't just inspect the static HTML, but also parse and execute JavaScript found on linked pages. Their goal is to prevent users from interacting with harmful sites, which is why they are so thorough. This proactive scanning is a crucial component in the arms race between blackhats and whitehats, as scammers increasingly use JavaScript for obfuscation or to trigger phishing forms.

It's an expected behavior for some mail servers to follow links as part of a security scan before delivering emails to the inbox. This is why you often see artificial clicks or opens from various ISPs (Internet Service Providers). These filters are trying to identify if a link leads to a malicious site or if the content on the linked page itself is dangerous. The execution of JavaScript is simply an extension of this security posture, aiming to catch dynamic threats.

The challenge arises because these systems are not actual human users. They don't intend to subscribe, click an unsubscribe link, or trigger any form actions. They are simply scanning for threats. When their scan accidentally completes an action, it distorts your data and can lead to unintended consequences, like a false opt-in.

The JavaScript dilemma

When you use JavaScript to auto-submit a form or redirect a user upon page load, you're essentially removing the explicit user action. For a security filter, there's no distinction between a human user visiting the page and the script running versus their automated system visiting the page and the script running. Both scenarios result in the form being submitted.

This can be particularly problematic for double opt-in processes where the confirmation is tied to a single click. If a filter clicks the link and the JavaScript immediately confirms the subscription, you lose the guarantee of a human intent to subscribe. This could also lead to issues with spam traps accidentally subscribing to your list, which can negatively impact your sender reputation.

JavaScript triggered action

A script on the landing page automatically submits the form or redirects the user as soon as the page loads. The user does not need to click a button.

Automation: Designed for convenience, removing an extra click.
Filter Behavior: Filters (e.g., Microsoft's) execute the JavaScript, leading to an unintended submission.
Data Accuracy: Skews opt-in rates, making it difficult to distinguish human from bot interactions.

The web standard for intentional user behavior is an explicit action, such as a button click, to initiate a POST request. JavaScript-triggered actions, while convenient, blur this line and are often problematic for security devices attempting to discern legitimate user intent from automated behavior.

Mitigating unwanted clicks and JS execution

To prevent email security filters from auto-clicking links and executing JavaScript in your opt-in emails, the most direct solution is to remove any JavaScript that triggers an automatic form submission or redirect upon page load. Instead, rely on an explicit user action, such as clicking a submit button.

While this might add an extra click for the subscriber, it ensures that an opt-in or confirmation is a deliberate action by a human. This approach provides more accurate data on actual user engagement and prevents unintended subscriptions caused by security scans. It also aligns with best practices for ensuring true consent.

Recommended approach

Manual user action

User Intent: Requires a direct click on a button or link to confirm subscription, indicating explicit consent.
Filter Resistance: Security filters primarily follow links; they are less likely to simulate a button click unless specifically programmed to do so after JavaScript execution. This is a common method for how to combat spam filter and bot clicks on emails.
Data Integrity: Provides more accurate data for analysis and filtering out bot clicks.

For even higher security and confirmation, you could consider implementing a system where the user has to enter a unique code (e.g., a six-digit code sent in the email) into a form field to confirm. This method significantly reduces the chance of automated systems accidentally confirming subscriptions because they cannot generate or copy the unique code.

Impact on email metrics and deliverability

Automated clicks from security filters can significantly skew your email metrics, leading to an inflated sense of engagement. You might see high click-through rates that don't translate into actual conversions or user activity. This false data makes it challenging to accurately assess campaign performance and optimize your email strategy. This phenomenon is why it's important to identify artificial email opens and clicks.

Beyond analytics, an unintended auto-confirmation of an opt-in can have deliverability implications. If these auto-confirmed addresses are invalid or become spam traps, they can harm your sender reputation. For instance, if a security filter auto-confirms a bot or spam address that later turns into a spam trap, your emails to that address will eventually bounce or lead to a blocklisting. This is why it's crucial to prevent bot clicks from hurting your reputation.

Moreover, if security checkers are actively modifying or breaking links or triggering unintended actions like one-click unsubscribes, it indicates an issue that needs to be addressed to maintain healthy email deliverability. Understanding what data supports filtering tools clicking on links in emails is key to diagnosing and solving these issues.

Views from the trenches

Best practices

Always prioritize explicit user actions over JavaScript auto-submissions for critical interactions like opt-in confirmations.

Monitor your engagement metrics closely for anomalies, such as high click rates from unexpected IP addresses or user agents.

Implement robust email authentication protocols, including SPF, DKIM, and DMARC, to enhance trust with email providers.

Common pitfalls

Relying solely on JavaScript for critical user actions, which can be easily misinterpreted or triggered by security filters.

Not segmenting or analyzing click data to identify and filter out automated bot clicks and artificial engagements.

Ignoring the signs of false opt-ins or unsubscribes, which can degrade list quality and sender reputation over time.

Expert tips

Consider adding a small delay to JavaScript-triggered actions if they are absolutely necessary, to give security scanners time to complete their scan without triggering the action.

For double opt-in, ensure the confirmation page requires a deliberate button press rather than an automatic form submission.

Regularly review your email logs for suspicious activity from known security scanner IP ranges to better understand their behavior.

Expert view

Expert from Email Geeks says security filters have been following links and checking for malicious content for a long time, often affecting open metrics and one-click unsubscribes, and that JavaScript is likely the cause of auto-submission issues.

2023-09-05 - Email Geeks

Marketer view

Marketer from Email Geeks says they should have expected headless rendering of web pages to become better over time, as running JavaScript is important for filters looking for phishing elements, even if it adds an extra step for subscribers.

2023-09-05 - Email Geeks

Navigating the automated landscape

While the behavior of email security filters auto-clicking links and running JavaScript can be frustrating for marketers, it's a necessary evolution in the ongoing battle against email-borne threats. These filters are simply doing their job to protect users from increasingly sophisticated phishing and malware attacks that rely on dynamic content and JavaScript.

For email marketers, the key is to adapt by prioritizing explicit user actions for critical processes like opt-in confirmations. By removing JavaScript that automatically triggers submissions or redirects, you can ensure that your engagement metrics are more accurate and that your subscriber list consists of genuinely interested individuals. This approach not only safeguards your deliverability and sender reputation but also fosters a healthier, more engaged audience.