Does email size affect spam trap triggers?

Key findings

• Spam trap hits: Are primarily a function of the recipient's email address and your list acquisition methods, not the content or size of your email.
• Spam filter influence: Email size can affect how spam filters evaluate your message. Overly large emails, especially those with minimal text or excessive code, may be flagged as suspicious.
• Deliverability impact: Large emails can slow down loading times and negatively impact user experience, which can indirectly lead to lower engagement and signal negative sender reputation to ISPs.
• Content balance: An imbalance, such as a high image-to-text ratio or large attachments, increases email size and can raise red flags for spam filters.

Key considerations

• Prioritize list hygiene: To prevent spam trap hits, rigorously clean your email lists and ensure all subscribers have provided explicit consent. For more on identifying these tricky addresses, refer to our guide on how to identify email spam traps.
• Optimize email size: While not a direct spam trap trigger, keeping your email file size under optimal limits (e.g., HTML under 100KB) can improve loading times and reduce the likelihood of spam filter scrutiny. Learn more about how email code quality and size impact deliverability.
• Balance content: Strive for a good balance between images and text. Avoid excessive imagery or large embedded elements that inflate file size without providing equivalent value.
• Monitor performance: Regularly check your email deliverability and engagement metrics. If you see dips, consider if content size or composition might be contributing to spam filtering. Email on Acid provides insights on how email file size affects deliverability.

Key opinions

• Spam trap cause: Marketers frequently point out that spam trap hits are solely due to issues with the email address itself (e.g., old, scraped, or unengaged addresses) and not the content within the email.
• Filter risk: A common concern is that overly large email sizes, particularly those heavy with images or complex code, can increase the likelihood of being caught by spam filters.
• User experience: Large emails can take longer to download and render, leading to a poor user experience that might result in lower engagement metrics and subsequent deliverability issues.
• Content quality: Some marketers suggest that large emails without significant text content are perceived as less legitimate by filters, indicating a need for balanced content.

Key considerations

• Strict list management: Implement robust processes for collecting and maintaining your email list to avoid problematic addresses. Consider our discussion on whether pristine spam traps are real for more insights.
• Content optimization: Focus on creating lean, efficient email designs. Reducing file size can prevent deliverability issues related to spam filters. If your emails are going to spam, our guide on why your emails are going to spam can help.
• Engagement focus: Ensure your email content is valuable and engaging to encourage opens and clicks, which positively influences sender reputation and deliverability, regardless of size.
• Testing: Regularly test your email campaigns across different clients and providers to catch any unexpected filtering due to size or content. MoEngage provides insights on how email file size affects deliverability.

Key opinions

• No direct link to spam traps: Experts consistently state that spam trap activation is about the destination address being a trap, completely independent of the email's content or its size.
• Spam filter consideration: Email size, particularly HTML exceeding a certain threshold (e.g., 100KB), can indeed be a factor for spam filters, potentially leading to increased scrutiny or outright blocking.
• Performance overhead: Larger emails can take longer to download and process, which can degrade the recipient experience and indirectly signal lower quality to ISPs, affecting future deliverability.
• Content imbalance warnings: Excessive image-to-text ratios or embedded elements that balloon email size can be perceived negatively by sophisticated spam filtering algorithms.

Key considerations

• Maintain list quality: The paramount consideration for avoiding spam traps is rigorous list hygiene and permission-based acquisition. If you're concerned about spam trap hits and deliverability, this should be your primary focus.
• Optimize content structure: While not directly for spam traps, optimize your email's HTML and CSS to reduce file size. This improves loading and parsing, enhancing overall deliverability. Monitor your DMARC reports for insights into filtering.
• Balance images and text: Ensure your emails have a healthy balance of text and images. Heavy images or complex layouts can increase file size and potentially trigger spam filters.
• Stay within size limits: As noted by Acoustic (referencing Litmus), keeping your HTML email size under 100KB is a good practice to avoid deliverability impacts related to file size. You can find more details on this topic on the Acoustic blog.

Key findings

• Trap mechanism: Spam trap technology is primarily designed to identify addresses that should not be on a mailing list, indicating list quality issues. Email content, including its size, is not typically part of the trap's detection logic.
• Filtering rules: Mailbox providers (ISPs) often have published guidelines or internal algorithms that consider email size as one of many factors in determining spam scores. Excessively large emails can trigger higher spam scores.
• Performance and user experience: Documentation suggests that emails with large file sizes may experience slower delivery and rendering, potentially leading to a negative user experience and reduced engagement, which indirectly harms sender reputation.
• Code and assets: Technical documentation often advises optimizing HTML, CSS, and image assets to minimize email file size, thereby improving loading times and reducing the chance of being flagged by filters.

Key considerations

• List compliance: Adhere strictly to consent-based email list practices to avoid hitting spam traps. This is the most crucial step for maintaining a clean sender reputation.
• Technical optimization: Ensure your email templates are coded efficiently and that images are compressed. Our article on how HTML email size and attachments affect deliverability offers further detail.
• Adhere to standards: While RFCs don't specify strict content size limits, adhering to general email standards helps ensure broad compatibility and proper rendering. Read more about what RFC 5322 says versus what actually works.
• Consult postmasters: Regularly check postmaster guidelines from major ISPs (like Gmail, Outlook, Yahoo) for their specific recommendations on email content, structure, and size to avoid filtering. Acoustic, referencing Litmus, provides relevant insights on email deliverability factors, including size.