How to protect email deliverability for image-only emails?
Michael Ko
Co-founder & CEO, Suped
Published 5 Jun 2025
Updated 19 Aug 2025
7 min read
Image-only emails can be tempting, especially when you want to use custom fonts or achieve a specific visual aesthetic. The idea is to create a striking, brochure-like experience for your subscribers. However, this approach carries significant risks for email deliverability, potentially leading to your carefully crafted messages landing in the spam folder instead of the inbox. I've seen many marketers face this challenge when prioritizing design over deliverability fundamentals.
The core issue lies in how email providers and spam filters interpret these messages. Without a substantial text component, your email can appear suspicious, resembling tactics often employed by malicious senders. Balancing design aspirations with robust deliverability practices is key to ensuring your campaigns reach their intended audience.
The inherent risks of image-only emails
When an email consists solely of images, it presents several challenges. Many email clients, by default, block images from loading to protect users from potential security risks or to save bandwidth. If your email is nothing but an image, subscribers will see a blank space, making your message unreadable and defeating its purpose. This can lead to decreased engagement and, consequently, lower sender reputation.
Furthermore, spam filters are designed to analyze email content for suspicious patterns. Image-only emails are a common characteristic of spam, as they can be used to bypass text-based filtering mechanisms. Without sufficient visible text, filters cannot properly scan the content for keywords or evaluate its relevance, increasing the likelihood of it being flagged as spam. This is a critical factor affecting whether your messages even make it to the inbox.
The spam filter dilemma
Email filters frequently flag emails with a very high image-to-text ratio as suspicious. This is because spammers often embed their entire message as an image to evade detection. If your email lacks enough readable text, it may be treated with increased scrutiny, potentially leading to its redirection to the spam or junk folder.
Beyond deliverability, image-only emails pose challenges for accessibility and user experience. Screen readers cannot interpret images without proper alt text, making your content inaccessible to visually impaired subscribers. Also, large image files can significantly increase email loading times, especially on slower connections, leading to frustration and abandoned opens. This is why many experts recommend avoiding image-only emails for better engagement and deliverability.
Best practices for balanced email design
To counter the risks associated with image-only emails, the most effective strategy is to incorporate a healthy balance of text and images. While the exact image-to-text ratio can vary, a common recommendation is to aim for at least 60% text content. This ensures that even if images are blocked, your core message remains legible and understandable. Including a substantial amount of text helps prove to spam filters that your email is legitimate content.
Using descriptive alt text for all your images is paramount. Alt text provides a textual description of an image, which is displayed if the image doesn't load. This not only aids accessibility for screen readers but also gives context to email clients and recipients. Make sure your alt text is concise, informative, and accurately describes the image's content. Additionally, always include clear and engaging preheader text, which often appears next to the subject line and can be crucial for enticing opens, even if images are off.
The image-only approach
Relying on a single, large image for the entire email body, often to achieve specific branding or custom fonts, overlooks how recipients view emails and how filters process them. This can lead to low readability for some users and higher spam scores. It also makes your emails look suspicious to some providers like Outlook or Gmail.
Balanced and robust email design
A better approach involves incorporating a good text-to-image ratio and designing emails to be responsive. This means using HTML text for critical information, headers, and footers, and leveraging images for visual appeal, supported by strong alt text. Consider slicing large images into smaller, more manageable pieces, allowing for more detailed alt text for each segment. This ensures content remains visible even with image blocking, and improves overall deliverability and user experience.
Finally, ensure your emails are designed to be responsive, adapting well to different screen sizes and email clients. A robust HTML structure with appropriate use of text, even for elements that are primarily visual, can significantly improve how your email is rendered and perceived by filters. Remember, the goal is to accompany images with text to convey your message effectively, whether images are displayed or not.
Technical considerations for image deliverability
Beyond content and design, underlying technical configurations play a vital role in protecting your email deliverability, especially when using image-heavy content. Proper email authentication, including SPF, DKIM, and DMARC, is non-negotiable. These protocols verify that your emails are legitimately sent from your domain, building trust with mailbox providers and reducing the likelihood of your messages being marked as spam or blocked outright.
The way you host and serve your images also impacts deliverability. While self-hosting images gives you control, ensure your hosting environment is reliable and fast. Using a Content Delivery Network (CDN) can improve image load times, but be mindful of your CDN's domain reputation, as a poor reputation can inadvertently affect yours. Always optimize image file sizes to minimize loading times and email weight, as excessively large emails can be viewed negatively by some providers.
Example of an image tag with effective alt textHTML
<img src="https://yourdomain.com/image.jpg" alt="A vibrant red apple with a green leaf, symbolizing freshness and health.">
Finally, pay attention to the HTML structure of your emails. Ensure clean, semantic HTML that supports responsive design. While the primary message might be image-based, always include a plain-text version of your email. This fallback is critical for recipients whose email clients do not display HTML or images, or for those who prefer plain text. A well-structured plain-text alternative can significantly contribute to your sender reputation and overall deliverability, as it ensures all subscribers can access your content.
Monitoring and testing for success
Even with best practices in place, continuous monitoring and testing are essential to maintain strong email deliverability, especially for campaigns with significant image content. Before sending any email, use an email testing tool to preview how your email renders across various email clients and devices. This helps you identify if images are loading correctly, if alt text is visible when images are blocked, and if the overall layout remains intact.
Regularly monitor your sender reputation and check if your sending IP or domain has been placed on any email blocklists (or blacklists). Being listed on a blocklist can severely hinder your deliverability, regardless of your email content. Use deliverability platforms to keep an eye on your sender score and identify any potential issues before they escalate. Pay close attention to spam complaint rates, as high rates can quickly damage your reputation.
Ensures accessibility and conveys message if images are blocked.
Authentication
Implement SPF, DKIM, and DMARC
Builds trust with ISPs, prevents spoofing, improves deliverability.
Email testing
Test rendering across various clients
Identifies display issues before sending to your list.
Monitoring engagement metrics, such as open rates, click-through rates, and unsubscribes, provides valuable insights into how your image-heavy emails are performing. Low engagement can signal deliverability issues or that your content isn't resonating. By continuously refining your strategy based on these metrics, you can ensure your image-rich emails not only look good but also consistently reach the inbox.
Views from the trenches
Best practices
Ensure critical information is always present as live HTML text, even if a large image serves as the main message. This provides fallback for image-blocked clients.
Use comprehensive and descriptive alt text for every image. This is crucial for accessibility and for conveying your message when images don't load.
Segment large images into smaller pieces if necessary to allow for more granular alt text and improve rendering across diverse email clients.
Always include a plain-text version of your email. This is a critical fallback for all recipients and filters.
Common pitfalls
Sending emails with only a single, large image without any accompanying HTML text, which can trigger spam filters and hinder accessibility.
Neglecting to include robust alt text for images, making the email unreadable if images are blocked by default in the recipient's email client.
Not optimizing image file sizes, leading to slow loading emails that can frustrate recipients and negatively impact engagement metrics.
Failing to regularly test how image-heavy emails render across various email clients and devices, leading to unexpected display issues.
Expert tips
Consider hiding additional text within the email body using CSS (like preview text) to increase your text-to-image ratio without altering the visual design.
Focus on maintaining a strong overall sender reputation through consistent engagement and good list hygiene, which can offset some risks of image-heavy content.
If using custom fonts is the main driver, explore modern email development techniques that allow for custom fonts with fallback options instead of relying solely on images.
Monitor your DMARC reports closely for any deliverability issues that might arise from content filtering, especially if you heavily rely on images.
Marketer view
A marketer from Email Geeks says that image-only emails are not ideal, but they typically do not directly kill deliverability if recipients have opted in.
2019-06-26 - Email Geeks
Marketer view
A marketer from Email Geeks says that including text in the footer and other sections, while using images for the main advertisement, is a good compromise.
2019-06-26 - Email Geeks
Striking the balance for email success
While image-only emails might seem like an appealing design choice, their impact on deliverability and user experience cannot be overlooked. Prioritizing visual aesthetics without considering the underlying mechanics of email delivery can lead to your messages being flagged as spam, blocked by clients, or simply not engaging recipients who cannot view your images.
By implementing a balanced approach that includes sufficient live text, descriptive alt text, proper authentication, and consistent monitoring, you can mitigate these risks. This ensures that your emails are not only visually appealing but also consistently reach their intended audience, fostering better engagement and protecting your sender reputation in the long run.
Outlook or 
Gmail.
