Does a high image to text ratio directly cause emails to go to spam?

While not as critical as it once was, a very high image-to-text ratio can still affect deliverability. Older spam filters, like SpamAssassin, may assign higher spam scores. Modern filters focus more on sender reputation and engagement, but excessive images can still raise flags, especially if combined with other suspicious characteristics. Email accessibility is also impacted without sufficient text.

What are the risks of sending image-only emails?

Email accessibility is severely impacted. If images are blocked or a recipient uses a screen reader, the core message of your email may be completely lost. This leads to a poor user experience, lower engagement rates, and can indirectly harm your sender reputation.

What is the recommended image to text ratio for emails?

You should aim for a balanced mix of text and images. While there isn't a universally perfect ratio, ensure your main message is conveyed through text. Use images to enhance, not replace, your message. Always include descriptive alt text for all images and optimize their file sizes to minimize load times.

Do large image file sizes affect email deliverability?

Yes, large image file sizes can impact deliverability. They increase the overall email size, which can lead to slow loading times, especially on mobile devices. Some inbox providers may also penalize or truncate emails that exceed certain size limits. Always optimize images for web to keep your email lightweight.

Are there other factors more important than image-to-text ratio?

Email spam filters assess numerous factors beyond content, including sender reputation, email authentication (SPF, DKIM, DMARC), and engagement metrics. If your emails consistently receive positive engagement (opens, clicks, replies) from a clean list, the impact of a higher image ratio is often minimized.

Does a high image to text ratio affect email deliverability and spam filtering? - Content - Email deliverability - Knowledge base

The question of whether a high image-to-text ratio affects email deliverability and spam filtering is a long-standing one in the email marketing world. For many years, the conventional wisdom strongly cautioned against image-heavy emails, often recommending a specific text-to-image ratio like 60/40. This advice was rooted in how older spam filters operated.

However, email deliverability is a dynamic field, constantly evolving as inbox providers and spam filters become more sophisticated. While the strict adherence to a specific image-to-text ratio might not be the primary factor it once was, it still plays a role, particularly for certain types of mailboxes and in conjunction with other email health indicators. Understanding this nuance is key to ensuring your emails consistently reach the inbox.

The evolving role of image to text ratio

Historically, spam filters struggled to interpret images, making image-only emails or those with very little text a potential red flag. Spammers would often embed their entire message within an image to bypass keyword-based text filters. This led to algorithms like SpamAssassin assigning higher spam scores to emails with a low text-to-image ratio. If an email consisted primarily of a single large graphic, it was more likely to be flagged.

Modern spam filters, however, have advanced significantly. They now analyze a much broader range of factors, including sender reputation, engagement metrics, email authentication (SPF, DKIM, DMARC), and content beyond just text. This means a high image-to-text ratio alone is less likely to be the sole reason an email lands in the spam folder compared to a decade ago.

Despite these advancements, the ratio still holds some weight, particularly with smaller ISPs or custom spam filtering setups that may not be as sophisticated as those used by larger providers like

Gmail or

Outlook. These systems might still assign a penalty for emails that appear to be overly reliant on images without sufficient textual content. Therefore, it is still a factor to consider for overall email health.

Why images can still be a concern

While not the sole determinant, several reasons explain why images can still contribute to deliverability issues (or at least not help). Large, unoptimized images increase the overall email size, which can slow down loading times, especially on mobile devices or slower connections. Some inbox providers may even rate-limit or reject excessively large emails. You should also consider how email image hosting affects deliverability.

Another critical aspect is accessibility. Many email clients block images by default, and users may have images turned off for various reasons. If your email is composed almost entirely of images, recipients who cannot see images will miss most, if not all, of your message. This leads to a poor user experience and can negatively impact engagement metrics, which in turn influences sender reputation and deliverability.

Image-only emails, while less of a direct spam trigger than before, can still be viewed suspiciously. Some spammers attempt to hide malicious content or links within images, which makes these types of emails a potential flag for filters. Without sufficient text, filters have less content to analyze for legitimate intent, leading to a higher risk of misclassification.

It is also worth noting that some email marketing platforms and older spam filters might still have built-in rules that disproportionately penalize emails with a very high image count or large image file sizes. While these are becoming less common, they still exist in some parts of the email ecosystem. Keeping a balance often hedges against these less sophisticated filters.

Best practices for using images in emails

To mitigate potential issues and ensure robust deliverability, focusing on a few key image best practices is crucial.

Bad practices

Image-only emails: Sending emails composed solely of images, especially without proper alt text, is a significant red flag for spam filters and accessibility. You can learn more about this on our page about image-only emails and deliverability.
Excessive image file sizes: Large images lead to slower load times and can increase the likelihood of your email being flagged or truncated by inbox providers.
Lack of alt text: Failing to provide descriptive alt text makes your email inaccessible when images are blocked or for users relying on screen readers.

Good practices

Balance text and images: Aim for a healthy balance, ensuring that your core message is conveyed even if images don't load. While there's no magic ratio, ensure meaningful text is present. Our page about the importance of the image to text ratio has more details.
Optimize image file sizes: Compress images without sacrificing quality to reduce email load times. Target under 100KB for the entire email.
Use descriptive alt text: Always include clear, concise alt text for all images. This ensures your message is conveyed even when images don't display.
Host images externally: Avoid embedding images directly within the email (Base64 encoding) as this significantly increases email size. Instead, link to images hosted on a reliable server. Our page on self-hosting email images can provide more guidance.

By following these practices, you can leverage the visual appeal of images while minimizing potential deliverability risks. Remember, email communication should prioritize clarity and accessibility for all recipients.

Beyond the ratio: reputation and engagement

Ultimately, what matters most for deliverability is your sender reputation and how recipients interact with your emails. If your audience consistently opens, clicks, and replies to your emails (even image-heavy ones), inbox providers will learn that your messages are desired and are less likely to flag them as spam. This engagement-based filtering is far more influential than any single content characteristic.

Focusing on building a positive sender reputation through consistent sending of wanted mail, maintaining a clean mailing list, and adhering to email authentication standards (SPF, DKIM, DMARC) will have a much greater impact than obsessing over an exact image-to-text ratio. You can find more information on how to fix common spam issues in our other guides.

However, ignoring content entirely is not advisable. Content analysis still plays a part, and egregious content choices, such as overly promotional language, spam trigger words, or suspicious links, will certainly harm your deliverability. The ideal strategy involves balancing visually appealing emails with clear, concise, and accessible textual content, all while nurturing a strong sender reputation.

Views from the trenches

Best practices

Always include alt text for all images to ensure accessibility and provide context even when images don't load.

Maintain a healthy balance of text and images so your core message is still readable without images.

Optimize all images for web use, compressing them to reduce file size without compromising quality.

Prioritize recipient engagement and sender reputation above rigid content rules, as these are more impactful.

Test your emails across various clients and devices to see how image rendering and text fallback behave.

Common pitfalls

Sending image-only emails where the entire message is embedded in a single image can trigger spam filters.

Using large, unoptimized image files increases email size and slows loading, potentially impacting deliverability.

Ignoring accessibility by not providing alt text or making emails unreadable without images.

Relying on outdated information about fixed image-to-text ratios instead of modern deliverability factors.

Focusing solely on content rules while neglecting critical sender reputation and authentication.

Expert tips

Consider that smaller ISPs and B2B mail servers might still rely on older filtering mechanisms, so a balanced ratio can be beneficial for those audiences.

If your audience is highly engaged and expects image-heavy emails, the deliverability impact might be minimal, as positive engagement can outweigh content flags.

Email is not a webpage; design for maximum accessibility and readability, even with images turned off or HTML disabled.

Regularly monitor your deliverability and inbox placement rates to understand how your specific email content performs.

Ensure your email authentication (SPF, DKIM, DMARC) is correctly configured, as this foundational element is crucial regardless of content.

Marketer view

Marketer from Email Geeks says that image-only emails can lead to deliverability issues at some ISPs.

2019-11-12 - Email Geeks

Expert view

Expert from Email Geeks says that SpamAssassin tests (like 'HTML has a low ratio of text to image area') indicate that a high image-to-text ratio can affect deliverability, especially with smaller receivers.

2019-11-12 - Email Geeks

Finding the balance

The belief that a high image-to-text ratio invariably leads to deliverability problems is largely a remnant of older spam filtering methodologies. While modern filters are far more sophisticated and prioritize sender reputation and engagement, image content still matters.

The key is to avoid extremes, prioritize accessibility with alt text, optimize image sizes, and ensure your emails offer value whether images load or not. A balanced approach, combined with strong sender reputation and engagement, will yield the best deliverability outcomes.