Does using images instead of text affect email deliverability?

Key findings

• Direct impact: Modern spam filters are sophisticated. The direct impact of using images for text on deliverability is often overstated and less of a primary concern than in the past.
• Accessibility: Images replacing text are a significant barrier for users relying on screen readers or those who have images blocked by default. Alt text is crucial but cannot fully replace actual text content.
• Engagement metrics: Emails that fail to render correctly or are inaccessible due to image-only content can lead to lower engagement (opens, clicks). This indirectly signals poor sender quality to mailbox providers, affecting future deliverability.
• Historical context: The concern originated when spammers used images to bypass text-based spam filters. While filters have evolved, the perception of image-heavy emails remains.

Key considerations

• Use alt text: Always provide descriptive alt text for images, especially when they contain critical information or replace text.
• Maintain text-to-image balance: Ensure a healthy balance between text and images. Avoid putting essential content exclusively within images. Learn more about if the image-to-text ratio is still important.
• Prioritize HTML text: Critical messaging and calls to action should be in live HTML text, not embedded in images, to ensure visibility and accessibility. This also protects deliverability for image-only emails.
• Test thoroughly: Test how your emails render across various email clients and devices, particularly how images scale and appear when blocked. You can find more detail on this topic in the Email on Acid article about text-to-image ratio.

Key opinions

• Avoid image-only emails: A common sentiment is to avoid emails composed entirely of images due to poor user experience, accessibility, and potential deliverability risks.
• Accessibility issues: Marketers highlight that images without corresponding text exclude users with visual impairments or those who block images, negatively affecting accessibility.
• Rendering challenges: Images often do not scale consistently across different mobile devices and email clients, making text embedded in images unreadable.
• Purpose of images: Images should amplify messaging and drive engagement, rather than replace critical text content. They are a design best practice, but should be used thoughtfully.

Key considerations

• Prioritize user experience: Ensure your email design is responsive and functional regardless of image loading, keeping the user's experience paramount.
• Strategic image use: Use images for visual appeal and engagement, but always include crucial information as plain HTML text to ensure good deliverability and accessibility.
• Optimize images: Compress images to reduce file size, improving load times and reducing the likelihood of them being flagged as suspicious. Chimp Essentials discusses the benefits and risks of using images.
• Address ESP limitations: If ESP editing limitations force image-based text, explore workarounds or consider platforms that offer greater customization to improve your overall deliverability.

Key opinions

• No direct OCR analysis: Experts largely agree that mailbox providers are unlikely to perform optical character recognition (OCR) on remote images for spam scoring due to the high computational cost.
• Accessibility over deliverability: The primary concern with image-based text shifts from direct spam flagging to the critical issue of accessibility for all users, including those with visual impairments or image blockers.
• Engagement feedback: Poorly rendered or inaccessible emails negatively affect user engagement, which is a key factor in long-term sender reputation and deliverability. This can also cause emails to go to spam.
• Outdated advice: Many commonly cited rules, such as rigid text-to-image ratios, are considered misguided or outdated by leading deliverability experts. High image to text ratios are not as impactful as they once were.

Key considerations

• Design for resilience: Emails should be designed to convey their message effectively even if images fail to load. This requires a strong textual foundation.
• Focus on content and reputation: Deliverability hinges more on sender reputation, content relevance, and consistent positive engagement than on the exact image-to-text balance.
• Use images appropriately: Images serve best as supplementary visual elements rather than containers for essential textual information. A resource like SpamResource.com emphasizes content quality.
• Educate clients: It's important to educate clients on current deliverability best practices and the risks associated with outdated approaches to email design.

Key findings

• Accessibility standards: Web content accessibility guidelines (WCAG), which apply to email, strongly recommend providing text alternatives for all non-text content, including images.
• HTML structure: Proper HTML markup and adherence to MIME types are foundational for emails to render correctly and be interpreted by email clients and spam filters.
• User engagement metrics: Mailbox providers' documentation emphasizes positive user interaction as a signal for good sender reputation, which can be negatively impacted by unreadable or broken image-only emails.
• Spam filter evolution: Documentation often alludes to the complexity of modern spam filtering, which considers sender reputation, authentication, and content relevance over simplistic image-to-text ratios.

Key considerations

• Implement alt text: Ensure all images include descriptive alt text to provide context for users who cannot view images or use assistive technologies. This is a core W3C accessibility principle.
• Provide plain text version: Always include a plain text version of your email. This improves accessibility and acts as a fallback if the HTML version doesn't render properly. Find out how a plain text version affects deliverability.
• Optimize image loading: Host images on reliable servers and optimize file sizes to ensure quick loading times, enhancing the user experience.
• Content diversity: Documentation encourages diverse content types to avoid appearing suspicious. This extends to technical aspects such as using UTF-8 encoding.