Can an email template trigger spam filters and cause deliverability issues?

Key findings

• Content is crucial: Email content, including the template's distinctive features, can indeed trigger spam filters.
• Image-to-text ratio: Emails that are primarily image-based (image slices) rather than text can sometimes be flagged, even with alt tags.
• Link quality: Issues like HTTP 429 errors (too many requests) on links within the email can signal problems to spam filters or frustrate recipients, leading to spam complaints.
• Testing tool limitations: Inbox placement testing tools may not always provide perfectly accurate results, and actual open rates (when tracking pixels fire) can contradict high spam placement predictions.
• Promotional context: Certain types of emails, like holiday sales, may inherently face tougher scrutiny or lower engagement due to recipient behavior.

Key considerations

• Review email content: Even with a good sender reputation, ensure your email copy and design avoid common spam trigger words and problematic formatting.
• Optimize template structure: Balance images with text, use clear HTML, and avoid overly complex designs that might be misinterpreted by filters.
• Validate all links: Ensure that all links within your email are functional and do not lead to errors or slow loading times, as this can negatively impact deliverability.
• Holistic troubleshooting: When diagnosing deliverability issues, consider all factors including sender reputation, content, and recipient engagement patterns (especially for seasonal campaign performance).

Key opinions

• Content is a common culprit: Many marketers find that changes in email content or template elements can directly lead to spam folder delivery.
• Image-heavy designs are risky: Emails composed primarily of image slices, even with proper alt tags and small file sizes, can be seen as suspicious by filters, raising concerns about deliverability.
• Promo tab vs. inbox: A lower open rate for promotional emails might be a normal outcome when they land in the promotions tab, rather than indicating a severe spam issue.
• Testing tool skepticism: Marketers express caution regarding the absolute accuracy of inbox placement tools, suggesting that real-world open rates can sometimes be a more reliable indicator.

Key considerations

• Design for deliverability: Careful email design is essential to ensure messages pass through spam filters. This includes balancing visual elements with sufficient text.
• Monitor real-world metrics: While testing tools offer insights, prioritize actual campaign performance metrics (like opens and clicks) to gauge true deliverability.
• Contextualize performance: Understand that open rates can vary significantly based on email type (e.g., welcome flow vs. promotional sales) and recipient behavior, especially during holiday seasons.
• Address underlying content issues: If deliverability drops with a new template or content, investigate potential spam trigger words, excessive imagery, or poor HTML that might be flagged by filters.

Key opinions

• Template influences content: Experts confirm that an email template significantly dictates the distinctive content features that spam filters scrutinize.
• Functional links are critical: If links within an email are problematic (e.g., returning 429 errors), it can render the email useless or annoying, leading to recipients marking it as spam.
• Open rate nuances: An email's open rate generally suggests it reached the inbox or a promotions tab, indicating that very high spam placement reported by testing tools might be inaccurate if there are opens.
• Testing tool limitations: The accuracy of probe accounts used by inbox testing tools is often questionable, and they may not reflect real-world filtering.

Key considerations

• Thorough link validation: Always verify that all links in your email template are fully functional and reliable to prevent deliverability issues and poor user experience. Broken links can contribute to email landing in spam folders.
• Contextualize testing results: Do not solely rely on the results of inbox testing tools. Cross-reference with your own metrics and real-world inbox checks.
• Consider seasonal impact: Account for seasonal changes in recipient behavior, which can affect open rates independently of spam filtering.
• Content and reputation synergy: Remember that content issues often have underlying reputation problems, requiring a holistic approach to deliverability troubleshooting. Mail that is considered spam is more likely to be added to a blocklist.

Key findings

• Content is a core factor: Spam filters examine email body content for suspicious characteristics, irrespective of sender reputation.
• Design matters: Poor email designs and unresponsive newsletter templates can directly break deliverability, signaling issues to ISPs and spam filters.
• Trigger words: Specific words and phrases often referred to as spam trigger words, such as "free" or "guaranteed", can activate spam filters.
• Image-to-text balance: An imbalance with too many images or specific font choices can lead to messages being filtered as spam.

Key considerations

• Content optimization: Regularly run email templates through spam filter tools to identify and fix potential issues before sending.
• HTML integrity: Ensure your email's HTML is clean and well-formed. Malformed HTML can negatively impact deliverability.
• Sender reputation synergy: Content problems, combined with a poor sender reputation, can exacerbate deliverability issues. Addresses on a blocklist or blacklist, for example, will see reduced deliverability.
• User interaction: Be aware that recipient actions, such as marking an email as spam, directly influence filter behavior and can lead to future emails being filtered.