Are image-based emails with alt text a viable strategy for email deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 16 Jul 2025
Updated 18 Aug 2025
7 min read
The question of whether image-based emails with alt text are a viable strategy for email deliverability is complex. On one hand, using images can offer creative freedom and ensure consistent rendering across different email clients, as what you design is largely what recipients see. This can be appealing, especially when dealing with the unpredictable nature of live text rendering.
However, relying heavily on images, even with proper alt text, introduces several challenges for email deliverability and accessibility. While alt text is crucial for providing context when images don't load or for users with screen readers, it doesn't fully replace live text in terms of user experience or spam filter evaluation.
Email service providers and mailbox providers have become highly sophisticated in detecting suspicious email patterns. An email composed almost entirely of images, even with alt text, can sometimes raise red flags, potentially impacting inbox placement. This is because spammers often use image-only emails to bypass text-based spam filters. Balancing visuals with sufficient live text is often the safest and most effective approach.
The role of alt text in deliverability
While alt text is a non-negotiable best practice for image-based emails, it serves primarily as a fallback. Its main purpose is to describe the image content for recipients whose email clients block images by default, or for those using screen readers due to visual impairments. This ensures that the message's core meaning is conveyed, even without the visual elements.Well-optimized alt text makes your emails accessible and readable. However, it does not magically transform an image-only email into a text-rich one in the eyes of spam filters.
Spam filters look for a healthy balance of text and images. An email with a disproportionately high image-to-text ratio, or one composed of a single large image, can be flagged as suspicious. This is a common tactic used by spammers to hide malicious content or phishing attempts within images, bypassing traditional content filters. Even if you include alt text, the overall structure can still trigger a blocklist (or blacklist) alert.
Therefore, while alt text is essential for accessibility and a good user experience, it's not a silver bullet for deliverability challenges associated with image-heavy emails. You still need to consider the overall image-to-text ratio and content balance.
The impact of user engagement
Mailbox providers prioritize user engagement heavily. If recipients consistently open, click, and interact positively with your image-based emails, even if they have a low text-to-image ratio, your deliverability may not suffer significantly. This is because positive engagement signals override many other potential flags. Conversely, if your image-heavy emails lead to low engagement, spam complaints, or unsubscribes, your sender reputation will decline, leading to more inboxing issues.
However, generating high engagement with image-only emails can be challenging. Images may be blocked by default in some email clients, and users on slow connections might not wait for large images to load. Without visible text, the user experience can degrade significantly, leading to less engagement. This is where the importance of a well-crafted plain text version comes into play, as screen readers and older clients often default to it.
I often see brands attempting to protect deliverability for image-only emails. If you're disciplined with other aspects of your email program, such as maintaining a clean list, managing sunsetting strategies, and not sending excessive emails, your overall sender reputation might be strong enough to offset some of the risks associated with image-heavy content. However, this doesn't mean image-only emails are inherently a good practice.
Some smaller email providers or enterprise spam filters (like SpamAssassin) may still factor in the text-to-image ratio directly into their filtering decisions. If you are struggling with emails going to spam, this could be a contributing factor, even if your audience's major mailbox providers are more forgiving.
Practical implications and best practices
Beyond deliverability, there are significant practical implications of relying solely on images for your email content. One major concern is accessibility. While alt text helps, it's not a full substitute for live text. Screen readers can struggle with complex image layouts, and users with certain disabilities may find image-only emails frustrating or impossible to navigate.
Another consideration is mobile responsiveness. Image-based text often doesn't scale as gracefully as live HTML text, leading to tiny, unreadable fonts on smaller screens, or images that break the email layout. This can lead to a poor user experience, increasing the likelihood of recipients deleting your email or even unsubscribing.
From a purely logistical standpoint, using live text generally offers more flexibility. It's easier to A/B test headlines or calls-to-action, make quick edits, or personalize content without needing graphic design resources for every minor change. A balanced approach allows for more agile campaign management.
I've often heard marketers talk about the efficiency of image-based emails. While it might seem like less work initially, the long-term impact on deliverability and user experience can lead to greater problems down the line. It's usually more efficient to invest in a robust email template that allows for easy content updates with live text.
A balanced strategy is key
Given these considerations, a purely image-based email strategy, even with alt text, is generally not recommended as a primary long-term approach for optimal email deliverability and user experience. While it might seem viable for brands with extremely high engagement or specific niche audiences, it carries inherent risks that can be avoided with a balanced strategy.
The ideal approach blends engaging visuals with sufficient live text, supported by a properly constructed plain text version. This ensures that your message is accessible, readable across devices and email clients, and less likely to trigger spam filters or blocklists. Your image to text ratio should always be considered.
Even for resource-constrained environments, investing in a flexible HTML template that accommodates both text and images will yield better long-term results for deliverability and overall campaign performance. This allows you to leverage the visual appeal of images while mitigating the risks associated with image-only content.
Views from the trenches
Best practices
Maintain a good balance between live text and images in your emails to ensure accessibility and cater to spam filters.
Always include descriptive alt text for all images to provide context for recipients with blocked images or using screen readers.
Ensure a robust plain text version of your multipart MIME message, as many email clients and assistive technologies will default to it.
Prioritize user engagement; positive interactions with your emails are a strong signal to mailbox providers, regardless of content style.
Common pitfalls
Relying solely on image-based emails can increase the risk of being flagged by spam filters, particularly by smaller or enterprise providers.
Forgetting that alt text, while crucial, does not fully replace the benefits of live text for deliverability and user experience.
Overlooking mobile responsiveness, as image-based text often does not scale well, leading to poor readability on smaller devices.
Neglecting the multipart MIME text version, which can significantly impact accessibility for users with assistive technologies.
Expert tips
While major B2C mailbox providers focus heavily on user interaction, some older or enterprise spam filters still consider the image-to-text ratio, so balance is key.
Image-only emails sacrifice significant accessibility, even with alt text. Always prioritize creating a proper text version.
Be aware that image alignment and arrangement can still be messed with by email renderers, so image-based emails are not a guaranteed formatting solution unless it's literally one large image.
Using a decent template for content and images can be more efficient than designing graphics for every email, variant, and edit.
Expert view
Expert from Email Geeks says that as long as recipients engage positively with the email, it being an image is not an issue, though user-friendly emails are better for engagement.
2024-03-01 - Email Geeks
Expert view
Expert from Email Geeks says that image-only emails sacrifice a lot of accessibility even with alt text and suggests creating a proper text version of the multipart MIME message. While some smaller mailboxes still use tools like SpamAssassin that consider text-to-image ratio, engagement is ultimately key, and image rendering can still be inconsistent.
2024-03-01 - Email Geeks
Conclusion
Ultimately, while image-based emails with alt text can offer some benefits in terms of consistent rendering and design control, they are not a universally viable strategy for optimal email deliverability. The inherent risks related to spam filtering, accessibility, and mobile responsiveness outweigh the perceived efficiencies for most senders. A balanced approach incorporating both rich visuals and sufficient live text remains the gold standard for reaching the inbox reliably and providing the best experience for your audience.
