Summary
While the image-to-text ratio is not the primary factor it once was for email deliverability, it still holds relevance. Modern spam filters are more sophisticated, prioritizing sender reputation and recipient engagement. However, an email composed entirely of images remains a significant red flag for deliverability, largely due to concerns about bypassing text-based filters, as well as posing accessibility challenges and poor user experience. While strict percentage rules are less critical, maintaining a balanced ratio, generally favoring more text, is still a recommended best practice to avoid triggering older or more aggressive content-based filters and ensure a positive experience for all recipients.
Key findings
- Reduced Primary Importance: The image-to-text ratio is no longer the primary determinant for email deliverability it once was, as modern spam filters have evolved to rely on more sophisticated metrics.
- Image-Only is a Red Flag: Emails consisting solely of images are consistently flagged as suspicious by spam filters, significantly harming deliverability due to concerns about bypassing text-based filters and accessibility issues.
- Influence on Some Filters: While not universally critical, an imbalanced, image-heavy ratio can still negatively impact deliverability by triggering older or more aggressive content-based spam filters.
- Sender Reputation is Key: Sender reputation and recipient engagement are far more critical influences on email deliverability than content-based factors like the image-to-text ratio.
- Accessibility & UX: Beyond deliverability, emails with insufficient text or that are entirely image-based pose accessibility challenges and result in a poor user experience if images are blocked or do not load.
Key considerations
- Avoid Image-Only Emails: Never send emails that are composed entirely of images, as this is a major red flag for spam filters and also compromises accessibility and user experience.
- Maintain Text Balance: Aim for a balanced text-to-image ratio, generally favoring more text, as this remains a recommended practice to prevent triggering content-based spam filters, especially older or more aggressive ones.
- Prioritize Reputation: Focus efforts on building and maintaining a strong sender reputation and fostering high recipient engagement, as these factors are far more influential on deliverability than the image-to-text ratio.
- Include Alt-Text: Always use descriptive alt-text for all images, not only for accessibility but also to provide context if images fail to load, which can improve the overall user experience.
What email marketers say
13 marketer opinions
The importance of the image-to-text ratio in email deliverability has undergone a transformation. While it's no longer considered the sole or even primary determinant by advanced modern spam filters, it retains relevance as a contributing factor for certain systems. Emails that are composed entirely of images remain a significant concern, consistently flagged as suspicious by filters, not only due to potential attempts to bypass text-based content analysis but also for accessibility and user experience issues. Experts widely agree that sender reputation and recipient engagement now exert far greater influence on deliverability outcomes. However, maintaining a thoughtful balance, generally favoring more text, is still advised as a fundamental best practice to avoid triggering older or more aggressive content-based spam filters and to ensure content is accessible to all recipients.
Key opinions
- Evolving Importance: The image-to-text ratio has a less critical role than in the past, as contemporary spam filters prioritize more sophisticated metrics such as sender reputation and engagement.
- Image-Only as a Flag: Emails consisting solely of images are a consistent red flag for spam filters, often leading to poor deliverability and impacting accessibility for users.
- Filter Sensitivity: While not universally applied, an imbalanced, image-heavy email can still negatively affect deliverability by triggering older or more aggressive content-based spam filters like SpamAssassin.
- Reputation Outweighs Ratio: Sender reputation and the level of recipient engagement are now far more significant drivers of email deliverability than the specific text-to-image proportions within an email.
- Recipient Experience: Beyond deliverability, a balanced image-to-text ratio contributes to better email accessibility and a more positive user experience, especially if images are blocked or fail to load.
Key considerations
- Avoid All-Image Emails: It is crucial to avoid sending emails composed exclusively of images, as this practice is highly likely to trigger spam filters and can hinder accessibility.
- Prioritize Text Content: Aim for a thoughtful balance that leans towards more text than images, which remains a widely recommended practice to enhance deliverability and ensure content clarity.
- Focus on Core Metrics: Allocate primary effort to building a robust sender reputation and fostering high subscriber engagement, as these factors are paramount for consistent email deliverability.
- Utilize Alt-Text: Always include descriptive alt-text for all images, improving accessibility for recipients and providing context even if images do not load correctly.
Marketer view
Email marketer from Email Geeks explains that for accessibility, alt-tags should always be filled and relevant. From experience, the text/images ratio isn't a strict deliverability criterion, though some anti-spam filters might still consider it.
3 May 2024 - Email Geeks
Marketer view
Email marketer from Email Geeks shares that while text/image ratio might still influence some content-based filters, deliverability is almost always more heavily influenced by sender reputation. He adds that large, well-known brands with good engagement frequently send image-only emails and generally achieve good deliverability.
16 Dec 2023 - Email Geeks
What the experts say
2 expert opinions
The significance of the image-to-text ratio in email deliverability has evolved, moving past its former role as a primary filter metric. While advanced spam filters no longer rely on simplistic ratio measurements, emails composed almost entirely of images with minimal text are still a concern. This is primarily because such designs can be used to circumvent text-based spam detection, and they also severely impact email accessibility and user experience when images are blocked or fail to load. Thus, the focus has shifted from a precise ratio to ensuring content is readable, accessible, and not designed to evade legitimate filtering.
Key opinions
- Advanced Filters: Modern email filters are highly sophisticated and no longer prioritize simplistic metrics like a fixed image-to-text ratio for deliverability.
- Image-Only Risk: Emails that are almost entirely image-based with very little text remain a significant red flag for mail filters.
- Bypass Detection: One reason all-image emails are flagged is their potential to bypass standard text-based spam filters, making them suspicious.
- Accessibility Impact: Beyond deliverability, emails lacking sufficient text create severe accessibility issues and offer a poor user experience, especially when images are not displayed.
- No Specific Ratio: There is no longer a specific problematic image-to-text ratio to avoid; the issue lies with the absence of meaningful text content.
Key considerations
- Avoid All-Image: It is crucial to avoid designing emails that are composed solely of images due to their high likelihood of being flagged by spam filters and for user experience reasons.
- Prioritize Text Content: Ensure your emails contain a substantial amount of visible text, improving both readability and deliverability.
- Focus on Accessibility: Design emails with accessibility in mind, providing textual content and appropriate alt-text for images to ensure a positive experience for all recipients.
- Beyond Simple Ratios: Shift focus from a precise image-to-text ratio to overall email design, ensuring it does not attempt to evade filters and provides clear, accessible content.
Expert view
Expert from Spam Resource explains that the email image-to-text ratio is no longer a primary filter metric for deliverability, stating that filters have advanced beyond relying on such simplistic measures. He clarifies that while maintaining a specific ratio is not important, entirely image-based emails should still be avoided due to accessibility issues and poor rendering when images are blocked, rather than for deliverability based on the ratio itself.
13 Apr 2023 - Spam Resource
Expert view
Expert from Word to the Wise explains that the image-to-text ratio is no longer as critical for email deliverability as it once was. While there isn't a specific problematic ratio, mail filters are still designed to detect emails that are almost entirely images with very little text. This is because such emails can be used to bypass text-based spam filters, and they also pose accessibility issues and result in a poor user experience if images fail to load.
30 Nov 2024 - Word to the Wise
What the documentation says
4 technical articles
While contemporary spam filters have advanced beyond solely relying on the image-to-text ratio, this factor still influences deliverability. Leading email service providers and deliverability experts emphasize that content which is heavily image-laden with minimal supporting text can still be flagged as spam. An imbalanced ratio continues to activate certain content-based filters, which can significantly impede an email's ability to reach the inbox.
Key findings
- Ratio Still Matters: An imbalanced image-to-text ratio, specifically one that is too image-heavy with insufficient text, remains a relevant factor for email deliverability.
- Triggers Spam Filters: Content-based spam filters analyze the image-to-text ratio, and excessive use of images with minimal text can significantly reduce deliverability by triggering these filters.
- Reduces Deliverability: Emails with an imbalanced, image-dominant content structure are frequently flagged as spam, leading to a higher likelihood of landing in spam folders.
- Industry Consensus: Leading email marketing platforms like Mailchimp, SendGrid, Litmus, and Constant Contact consistently advise maintaining a balanced ratio to enhance deliverability and avoid spam flagging.
Key considerations
- Balance Visuals and Text: Strive for a balanced ratio of images to text in your emails, ensuring there is sufficient textual content to complement your visuals and convey your message effectively.
- Avoid Image-Heavy Content: Refrain from designing emails that are excessively image-heavy with insufficient supporting text, as this disproportion can still trigger content-based spam filters.
- Prioritize Core Message in Text: Ensure that your email's primary message, call to action, and key information are clearly conveyed through text, rather than relying solely on images.
- Adhere to ESP Guidelines: Follow the recommendations from leading Email Service Providers regarding content balance, as they consistently advise against overly image-dominant emails for improved deliverability.
Technical article
Documentation from Mailchimp Knowledge Base advises that a balanced text-to-image ratio is important for email deliverability, recommending against content that is too image-heavy with insufficient text, as this can cause an email to be flagged as spam.
23 Oct 2021 - Mailchimp Knowledge Base
Technical article
Documentation from SendGrid Blog explains that content-based spam filters analyze factors like the image-to-text ratio, and an excessive use of images with minimal text can significantly reduce deliverability by triggering these filters.
2 Sep 2024 - SendGrid Blog
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