Do image-only emails still affect email deliverability?

While not as heavily penalized as in the past, entirely image-based emails can still face deliverability issues due to large file sizes, slow loading times, and detection by less sophisticated spam filters. Modern filters prioritize sender reputation and engagement over content ratios, but issues with images can still indirectly impact deliverability by leading to poor recipient engagement.

Why are image-based emails bad for accessibility?

Image-based emails are poor for accessibility because screen readers cannot interpret images without proper alt text . If images are blocked or don't load, users on slow connections or those with visual impairments will see a blank or uninformative email, hindering their ability to understand your message.

What are the best practices for using images in emails?

To mitigate risks , always include descriptive alt text for images, optimize image file sizes (aim for total email size under 100-200KB), and ensure that crucial information and calls to action are also present as live HTML text. This creates a fallback for when images don't load.

Is the image-to-text ratio still important for deliverability?

While email authentication (like DMARC, SPF, DKIM) and sender reputation are now primary factors, the image-to-text ratio can still play a role for some legacy or less advanced spam filters. More importantly, it impacts user experience, which indirectly affects engagement and thus deliverability.

Are image-based emails a good practice, and what are the deliverability and accessibility implications? - Content - Email deliverability - Knowledge base

I’ve noticed a growing trend where more and more companies, especially in e-commerce, seem to be adopting emails that are almost entirely image-based. It makes me wonder if these brands are prioritizing visual appeal and branding over raw performance metrics like deliverability. It's an interesting shift, and I'm keen to explore the actual implications.

The traditional wisdom around email design often advised against heavy reliance on images due to concerns about spam filters and accessibility. However, with the evolution of email technology and recipient behavior, it's worth re-evaluating if these concerns still hold the same weight. Are email providers still heavily penalizing image-heavy emails, or has the landscape changed?

The shifting landscape of email filtering

The email deliverability landscape has significantly evolved. While older spam filters often flagged emails based on a high image-to-text ratio, the focus has largely shifted. Modern spam filters and mailbox providers are far more sophisticated, relying heavily on sender reputation and engagement metrics, bolstered by robust authentication protocols like DMARC, SPF, and DKIM.

This means that if your domain has a strong reputation, backed by proper authentication, the content itself, including the proportion of images, might have less direct impact on whether it lands in the inbox or a spam folder. The recipient's actions, such as opening, clicking, or marking as spam, now play a much larger role in determining future deliverability.

However, it is crucial to remember that some smaller, less sophisticated email hosting services (and their associated spam filters) might still assign weight to the image-to-text ratio. Therefore, while major providers have moved past it, a completely image-based email could still encounter deliverability hurdles with certain recipients.

Content vs. engagement

The truth behind image-to-text ratio is that content structure has less bearing on deliverability today. Instead, focus on positive engagement signals. If recipients frequently mark your image-only emails as spam, your overall sender reputation will suffer, regardless of your image-to-text ratio.

Deliverability concerns with image-heavy emails

Even with advanced filters, image-heavy emails still carry certain deliverability risks. The most significant concern is the overall file size. Emails with large images can take longer to load, especially for recipients on slower internet connections or mobile data. This can lead to a poor user experience, potentially causing recipients to abandon the email or, worse, mark it as spam.

Large images can also trigger certain spam filters that are sensitive to oversized messages, increasing the chance of your email being directed to the junk folder. This is less about the image-to-text ratio itself and more about the technical overhead and potential for a negative user experience.

Another factor is how the images are hosted. While many email service providers (ESPs) host images for you, some senders choose to self-host email images. If the image host is unreliable or associated with malicious activity, it can negatively impact your email's deliverability, even if your domain reputation is otherwise good. This means your email could land on a blocklist (or blacklist) simply due to issues with the image source.

Image-only emails

File size: Often larger, leading to slow loading times and potential flagging by spam filters, potentially causing deliverability issues.
Preview text: Often blank or irrelevant if no text is present.
Image blocking: If images don't load, the email appears empty, missing the entire message.

Balanced emails (text + images)

File size: Optimized for faster loading and reduced spam flagging.
Preview text: Provides a clear summary to entice opens.
Image blocking: Text content remains visible, conveying the message even without images.

The critical impact on accessibility

Beyond deliverability, the most significant drawback of image-based emails is their severe impact on accessibility. Many users rely on screen readers or have images disabled by default in their email clients for various reasons, including data saving or security preferences. A purely image-based email provides no readable content for these users, rendering your message completely inaccessible.

This is where alt text becomes critical. Alt text (alternative text) provides a textual description of an image, which screen readers can interpret and display when images are blocked. Without meaningful alt text, an image-heavy email is essentially a blank canvas to a significant portion of your audience, negating any brand or marketing message you intended to convey.

Example of proper alt text in HTMLhtml

<img src="your-image.jpg" alt="A group of people collaborating on a project, smiling and engaged.">

Beyond alt text, consider the overall design. Ensure that critical information, calls to action, and key messages are present as live, selectable text. This guarantees that your email's core purpose is conveyed, even if images fail to load or are not viewed. Remember, accessible emails are not just about compliance, but about reaching your full audience effectively.

Balancing visuals and performance for optimal results

Images undoubtedly enhance email aesthetics and user engagement. They can quickly capture attention, convey complex ideas visually, and strengthen brand identity. The goal isn't to avoid images, but to use them strategically and in conjunction with text to create a resilient and impactful email.

Maintaining a healthy balance between images and text is still a best practice. While the image-to-text ratio might not be the primary deliverability factor it once was, it remains a common consideration for some filters and, more importantly, for providing a robust user experience across all email clients and conditions.

Focus on optimizing image file sizes to keep the overall email lightweight. Compress images without compromising quality, and consider using modern image formats where supported. Ensure your calls to action are prominent and clickable, whether as part of an image or, ideally, as bulletproof HTML buttons with live text overlays.

Aspect	Best practice for images
File size	Keep total email size under 100-200KB, compress images.
Alt text	Always provide descriptive alt text for all meaningful images.
Text-to-image ratio	Aim for a good balance, ensuring key messages are in live text.
CTAs	Use bulletproof buttons with live text instead of image-only buttons.

Views from the trenches

Best practices

Ensure critical information is always conveyed through live text, not just images.

Utilize descriptive alt text for all images to support accessibility and when images don't load.

Keep email file sizes optimized by compressing images to improve loading times and deliverability.

Common pitfalls

Relying solely on images, which can lead to blank emails if images are blocked.

Ignoring accessibility, making emails unusable for screen reader users.

Using unoptimized, large image files that slow down loading and trigger spam filters.

Expert tips

Email providers are focusing more on sender reputation and engagement signals over old content rules.

Modern email authentication protocols mitigate some content-based filtering risks.

Consider that some smaller email hosting services still use older image-to-text ratio weighting.

Expert view

Expert from Email Geeks says the trend of 100% image-based emails might not be as universal as perceived, and the adoption of robust authentication protocols means image-heaviness matters less, as recipients themselves become content filters.

2021-03-12 - Email Geeks

Marketer view

Marketer from Email Geeks says that image-only emails are still a bad idea, despite any perceived trends.

2021-03-12 - Email Geeks

Striking the right balance

While the impact of images on email deliverability has shifted over time, image-based emails are not inherently a good practice when used exclusively. They introduce significant accessibility challenges and can still create deliverability hurdles, especially concerning file size and fallback content. The perceived trend of more image-only emails in certain sectors might be driven by ease of creation or a misconception about current filtering mechanisms.

Ultimately, the key is balance. Strategic use of images, combined with robust text content and proper accessibility considerations, will lead to better deliverability and a superior user experience for all recipients. Prioritize clear messaging, optimize your visuals, and ensure your emails are resilient enough to convey their message even when images don't load. This approach is fundamental to improving email deliverability in today’s complex email ecosystem.