Summary
Sending emails composed solely of images presents significant deliverability challenges, as spam filters are largely unable to interpret visual content. This lack of readable text makes such emails appear suspicious, often leading to them being flagged as spam by various inbox providers, including major players like Gmail. To counteract this, email marketers must implement specific strategies that balance visual appeal with filter-friendly content.
Key findings
- Filter Inability to Read Images: Spam filters cannot directly read or interpret content embedded within images, making image-only emails inherently suspicious and prone to being flagged.
- Increased Spam Flagging: Emails primarily composed of images are frequently identified as red flags by anti-spam systems, severely increasing the likelihood of landing in the spam folder.
- Inbox Provider Scrutiny: Major inbox providers, especially Gmail, are increasingly wary of and aggressively filter image-heavy or image-only emails, as these formats are commonly abused by spammers for malicious purposes like phishing.
- Reputation Impact: A lack of searchable, text-based content can negatively impact an email sender's reputation points with providers that use content analysis for targeted advertising and deliverability scoring.
Key considerations
- Optimal Text-to-Image Ratio: Prioritize a healthy text-to-image ratio, with recommendations often ranging from 60-40% to 80-20% text, ensuring that the primary message is conveyed through readable text.
- Descriptive Alt Text: Always include descriptive alt text for all images. This not only aids accessibility for recipients with images turned off but also provides crucial textual context for spam filters.
- Plain Text Version: Provide a comprehensive plain text version of every email. This alternative ensures readability across all email clients and offers a fallback for filters that might struggle with HTML.
- Text-Based Essential Content: Ensure that critical elements such as footers, calls to action, physical addresses, and unsubscribe links are rendered as visible text, rather than being part of an image.
- Strategic Image Use: Use images to complement and support text content, rather than replacing it. If images are crucial, consider slicing them to allow for more granular alt text application and ensure proper HTML formatting.
What email marketers say
13 marketer opinions
Protecting email deliverability when using significant imagery requires a proactive approach, centering on making content accessible and readable for automated spam filters. Since these filters cannot interpret images, integrating sufficient textual elements is paramount to signal legitimacy and ensure messages reach the inbox. Adopting a balanced approach, where images enhance rather than dominate the message, is key to navigating the intricacies of modern email filtering systems.
Key opinions
- Text-to-Image Balance: Maintaining a healthy text-to-image ratio, with recommendations often suggesting a minimum of 40% text and ideally higher, is a critical factor for email deliverability.
- Mandatory Alt Text: The consistent use of descriptive alt text for all images is not only vital for accessibility but also provides readable content cues for spam filters to interpret image context.
- Plain Text Version Requirement: Always including a robust plain text version alongside HTML emails ensures content readability for all email clients and provides a crucial fallback for sophisticated spam filters.
- Visible Textual Content: Beyond images, emails must contain substantial visible text, including body copy, physical addresses, and clear unsubscribe links, to be properly analyzed and deemed legitimate by spam filters.
- Hidden Text Strategy: Incorporating hidden text elements, such as specific preview text, can serve as an additional measure to increase the overall text content and mitigate deliverability risks.
Key considerations
- Prioritize Textual Content: Ensure the email's core message, calls to action, and critical information are conveyed through readable text, not solely within images, to enable spam filter analysis.
- Optimize Text-to-Image Ratio: Aim for a text-to-image balance that favors text, with experts suggesting ratios ranging from 60% text to 40% images up to 80% text to 20% images for improved deliverability.
- Implement Comprehensive Alt Text: Consistently apply descriptive alt text to all images. This serves as a vital textual fallback for email clients that block images and provides context for spam filters.
- Always Provide Plain Text Version: Include a complete plain text version of every email. This critical component ensures broad compatibility and offers an unformatted alternative that spam filters can easily process.
- Ensure Text-Based Footer Elements: Place essential footer information, such as physical addresses and unsubscribe links, as text rather than embedding them in images to ensure they are readable by filters and compliant.
Marketer view
Email marketer from Email Geeks explains that Gmail might penalize emails lacking searchable content for targeted ads, potentially affecting reputation points. He recommends ensuring proper ALT text and a text-based footer.
18 Sep 2022 - Email Geeks
Marketer view
Email marketer from Email Geeks states that text-to-image ratio is a deliverability factor and suggests including a hidden text version (like preview text) to mitigate this.
8 Mar 2023 - Email Geeks
What the experts say
4 expert opinions
While some experts suggest that image-only emails may not directly harm deliverability for highly engaged, opted-in users, the overwhelming consensus is that such content poses a substantial risk. Inbox providers, particularly Gmail, are increasingly wary of and aggressively filter emails that are primarily images, often associating them with spamming tactics. To safeguard deliverability, it is essential to prioritize a healthy text-to-image ratio, ensuring the core message is conveyed through text, and always include descriptive alt text for all images. Additionally, crucial elements like footers and unsubscribe links should always be in text format.
Key opinions
- High Deliverability Risk: Sending emails composed predominantly or entirely of images is widely considered a significant risk to deliverability, often leading to messages being flagged as spam.
- Inbox Provider Scrutiny: Major inbox providers, especially Gmail, are highly vigilant against image-heavy or image-only emails due to their frequent use by spammers, aggressively filtering such content.
- Text-to-Image Ratio Importance: A healthy text-to-image ratio is paramount, as it helps email filters understand the content and reduces the likelihood of an email being marked as suspicious.
- Alt Text for Context: The inclusion of alt text for images not only serves accessibility purposes but also provides valuable textual context for spam filters, which cannot 'read' images directly.
Key considerations
- Prioritize Textual Content: Ensure that the primary message, calls to action, and all vital information are conveyed through readable text, not solely within images, to aid spam filter analysis.
- Optimize Text-to-Image Balance: Aim for a high text-to-image ratio, with experts often suggesting percentages like 60-40% or 80-20% text, to signal legitimacy to inbox providers.
- Implement Comprehensive Alt Text: Consistently apply descriptive alt text to all images, as this provides crucial textual context for spam filters and improves accessibility for recipients.
- Use Text for Crucial Elements: Ensure essential email components, such as footers, physical addresses, and unsubscribe links, are rendered as text rather than embedded in images.
- Consider Image Slicing: For designs that are necessarily image-heavy, consider slicing images into multiple pieces, which can allow for more granular alt text application and potentially better HTML rendering.
Expert view
Expert from Email Geeks explains that sending image-only emails is not ideal but will not directly harm deliverability, especially for opted-in users. She suggests using text for footers and other non-advertisement content.
25 Jun 2022 - Email Geeks
Expert view
Expert from Email Geeks suggests slicing images into multiple pieces to allow for more ALT text, which is beneficial for recipients with images turned off.
23 Sep 2022 - Email Geeks
What the documentation says
3 technical articles
Major inbox providers, including Gmail and Microsoft's Exchange Online Protection, along with services like Amazon SES, consistently underscore the importance of text-based content to protect email deliverability. Their guidelines strongly suggest that emails relying exclusively on images, especially without proper formatting or a plain-text alternative, are highly susceptible to being flagged by spam filters. These systems actively analyze content for patterns, and a lack of readable text in image-dominant emails raises suspicion, increasing the likelihood of messages being filtered out or sent to the spam folder.
Key findings
- Provider Warnings on Image Dependence: Major providers like Google, Microsoft, and Amazon SES warn that emails heavily reliant on images, especially without text, risk deliverability due to filter limitations.
- Plain-Text is Non-Negotiable: The provision of a plain-text alternative is consistently recommended by all major platforms as essential for ensuring content accessibility and proper filter processing.
- Content Scrutiny by Filters: Spam filters conduct heuristic analysis, flagging emails that lack sufficient textual content or use images in suspicious patterns often associated with phishing.
- Ratio and Formatting Influence: A healthy text-to-image ratio and correct HTML formatting that ensures content is accessible, not hidden, are key factors influencing filter assessment and deliverability.
Key considerations
- Always Provide Plain-Text Alternative: Crucially, always include a comprehensive plain-text version for every HTML email to ensure content readability for all recipients and email filtering systems.
- Prioritize Textual Content: Design emails so that the primary message and crucial information are conveyed via text, not embedded solely within images, to aid filter interpretation.
- Optimize Text-to-Image Balance: Maintain an appropriate balance, ensuring enough visible text accompanies images to signal legitimacy and avoid triggering content-based spam filters.
- Apply Correct HTML Formatting: Use proper HTML to ensure all content, including text elements, is accessible and not obscured or hidden within image files, which can raise red flags.
Technical article
Documentation from Google's Gmail Bulk Sender Guidelines implicitly suggests that highly image-dependent emails, especially those without proper formatting or a plain-text alternative, can impact deliverability. They recommend creating a plain-text version to ensure readability and emphasizing correct HTML formatting, which includes making content accessible rather than hidden within images.
7 May 2025 - Google Gmail Bulk Sender Guidelines
Technical article
Documentation from Microsoft Learn, concerning Exchange Online Protection (EOP), implies that image-only emails without sufficient textual content can be flagged by spam filters due to their heuristic analysis of email content. EOP's anti-spam policies analyze content for suspicious patterns; emails solely relying on images, especially those used in phishing, are at higher risk of being filtered out.
23 Jun 2022 - Microsoft Learn
Are image-only emails bad for deliverability?
Do images in email and PDF attachments affect email deliverability?
Do images in emails affect deliverability?
Does using images instead of text affect email deliverability?
How can I improve email deliverability for large emails with many images and links when experiencing high spam complaint rates?
How can I improve my email deliverability?
