Does email size affect spam trap triggers?

Summary

Experts, marketers, and documentation agree that email size does *not* directly trigger spam traps. Spam traps are triggered by sending to specific addresses, often related to list hygiene. However, email size *indirectly* affects deliverability. Large emails, especially those with poorly coded HTML and large attachments, can lead to slower loading times, rendering issues, and a poor user experience. This can increase the likelihood of recipients marking the email as spam, harming sender reputation and potentially increasing spam scores. Mail servers often impose size limits, and exceeding these will result in message rejection/bounce. Optimizing code, compressing images, and keeping email size within reasonable limits (e.g., 102KB or less) are crucial for maintaining good deliverability.

Key findings

  • No Direct Spam Trap Trigger: Email size does not directly trigger spam traps; the destination address is the primary factor.
  • Indirect Impact on Deliverability: Large emails can indirectly harm deliverability due to slower loading, rendering issues, and poor user experience.
  • Server Size Limits: Mail servers impose size limits; exceeding these results in message rejection.
  • Code and Content Matters: Poorly coded HTML and large attachments contribute to deliverability problems.
  • User Perception Affects Spam: Negative user experience (rendering issues, slow loading) increases the chance of being marked as spam.

Key considerations

  • List Hygiene: Maintain good list hygiene practices to avoid hitting spam traps, as this is the primary trigger.
  • Email Size Optimization: Keep email size within reasonable limits (e.g., under 102KB) for optimal deliverability and user experience.
  • Code and Image Optimization: Optimize HTML code and compress images to reduce email size and improve rendering.
  • Attachment Strategy: Consider linking to large files instead of embedding them as attachments.
  • User Experience Focus: Prioritize a positive user experience by ensuring emails load quickly and render correctly on various devices.

What email marketers say
10Marketer opinions

While email size itself doesn't directly trigger spam traps, it significantly impacts email deliverability. Larger emails can lead to slower loading times, rendering issues across different email clients, and a poorer overall user experience. These factors can increase the likelihood of unsubscribes or recipients marking emails as spam, ultimately harming sender reputation. Optimizing code, compressing images, and keeping overall email size below recommended thresholds (e.g., 102KB) are essential for maximizing deliverability. Focus should be on a clean design, optimized code, and user experience.

Key opinions

  • Direct Trigger: Email size does not directly trigger spam traps.
  • Deliverability Impact: Large emails negatively impact deliverability due to longer loading times, rendering issues, and potential timeouts.
  • User Experience: Poor user experience (slow loading, rendering issues) increases the likelihood of being marked as spam.
  • Spam Score: Overly large emails with messy code can increase spam scores due to perceived unprofessionalism and rendering problems.
  • Attachments: Large attachments are more likely to trigger spam filters than the size of the HTML content itself.

Key considerations

  • Email Size Limit: Keep email size under recommended limits (e.g., 102KB) for optimal deliverability.
  • Image Optimization: Optimize images and consider linking to files hosted online to minimize email size.
  • Code Optimization: Use clean, well-coded HTML to reduce email size and avoid rendering issues.
  • User Experience: Focus on providing a positive user experience to avoid recipients marking emails as spam.
  • Attachments: When adding attachments, consider linking to them instead of embedding them directly in the email.
Marketer view

Email marketer from Gmass explains that large emails with heavy images can slow down deliverability. While it doesn't directly trigger spam traps, it may impact the time it takes for email to get delivered. Spam emails should be avoided by keeping the email short.

November 2023 - Gmass
Marketer view

Email marketer from StackOverflow clarifies that large attachments are more likely to trigger spam filters than the size of the HTML content itself. Optimize images and consider linking to files hosted online to minimize size.

September 2024 - StackOverflow
Marketer view

Email marketer from Sendinblue Blog recommends keeping email size under 102KB for optimal deliverability. Larger emails can be flagged as spam by some providers and lead to rendering issues across different email clients, decreasing overall ROI.

July 2022 - Sendinblue Blog
Marketer view

Marketer from Email Geeks shares that content is not related to spam traps, but data is. Hitting spam traps relates to list collection and hygiene.

January 2025 - Email Geeks
Marketer view

Email marketer from EmailOctopus Blog shares that excessively large emails can negatively affect deliverability due to longer loading times and potential for timeouts. While not directly triggering spam traps, this can still harm your sender reputation.

May 2022 - EmailOctopus Blog
Marketer view

Email marketer from Reddit explains that while email size itself might not trigger spam traps, overly large emails with messy code can increase spam scores due to perceived unprofessionalism and potential rendering issues. Focus on clean code and optimized images.

October 2024 - Reddit
Marketer view

Email marketer from Litmus suggests focusing on a good user experience as large emails can cause rendering problems in some email clients. These issues don't directly trigger spam traps, but can lead to recipients marking emails as spam due to poor experience.

October 2022 - Litmus
Marketer view

Email marketer from MailerCheck explains that keeping your email size down is crucial for ensuring faster loading times and a better user experience. While the size itself might not trigger spam traps, a poor user experience can increase the likelihood of users marking your emails as spam.

November 2021 - MailerCheck
Marketer view

Email marketer from Email Marketing Forum advises that complex HTML and large images can inflate email size and potentially increase spam scores. While not directly triggering traps, higher scores can affect deliverability.

September 2021 - Email Marketing Forum
Marketer view

Email marketer from Mailjet Blog explains that while email size doesn't directly trigger spam traps, larger emails can impact deliverability. Larger sizes contribute to slower loading times and a poorer user experience, increasing the likelihood of unsubscribes or being marked as spam.

March 2024 - Mailjet Blog

What the experts say
2Expert opinions

Experts agree that email size does not directly trigger spam traps. Spam traps are primarily hit based on the destination email address. However, large emails, especially those with poorly coded HTML, can negatively affect deliverability, leading to emails being filtered or experiencing rendering issues. Proper email coding practices are important.

Key opinions

  • Spam Trap Trigger: Email size does not directly trigger spam traps; destination address is the key factor.
  • Indirect Impact: Large emails with bad HTML can contribute to deliverability problems.
  • Filtering and Rendering: Large, poorly coded emails are more likely to be filtered or have rendering issues.

Key considerations

  • Proper Coding: Employ proper email coding practices to ensure deliverability.
  • Email Size Optimization: Keep email size manageable to avoid potential deliverability issues, even if it doesn't directly trigger spam traps.
Expert view

Expert from Email Geeks explains that spam trap hits are determined by the destination address, not the content or size of the email.

September 2023 - Email Geeks
Expert view

Expert from Word to the Wise, Laura Atkins, explains that while email size doesn't directly hit spam traps, excessively large emails with badly coded HTML can contribute to deliverability issues, making them more likely to be filtered or have rendering problems. Proper email coding is key.

August 2021 - Word to the Wise

What the documentation says
4Technical articles

Technical documentation indicates that while SMTP standards and IETF specifications do not impose hard limits on email size, mail servers like Gmail and Exchange Online enforce practical size limits. Exceeding these limits results in message rejection or bounces, but email size does not directly trigger spam traps.

Key findings

  • No Direct Trigger: Email size does not directly trigger spam traps according to documentation.
  • Practical Limits: Mail servers impose practical size limits despite the lack of hard limits in standards.
  • Rejection/Bounce: Exceeding server-imposed limits results in message rejection or bounce.

Key considerations

  • Adhere to Limits: Adhere to the email size limits set by receiving mail servers to avoid rejection.
  • Size vs. Traps: Focus on other deliverability factors, as size does not directly trigger spam traps.
Technical article

Documentation from RFC Editor specifies that SMTP standards do not impose a hard limit on email size, but practical considerations by servers often lead to size restrictions. Exceeding these limits may result in rejection, though it doesn't directly trigger spam traps.

May 2022 - RFC Editor
Technical article

Documentation from Microsoft Support states that Exchange Online has message size limits that can be configured by administrators. Reaching those limits will cause the message to bounce, but does not directly cause spam traps.

June 2022 - Microsoft Support
Technical article

Documentation from IETF specifies that there are no size restrictions on message bodies in the RFC, however, practical limitations are imposed by the receiving mail systems. Reaching those limits will cause the message to bounce and/or not send correctly, but does not directly cause spam traps.

July 2024 - IETF
Technical article

Documentation from Google Workspace Admin Help indicates that Gmail has a message size limit of 25 MB, including attachments. Exceeding this limit will prevent the email from being sent, but doesn't directly interact with spam traps.

March 2021 - Google Workspace Admin Help