The question of whether images in emails affect deliverability is a common one, and the answer isn't a simple yes or no. For many years, email marketers have been told that a high image-to-text ratio could land their emails in the spam folder, leading to cautious approaches to email design.
The landscape of email deliverability is constantly evolving. While older spam filters might have been easily tricked by image-only emails used by spammers, modern email service providers (ESPs) and internet service providers (ISPs) use much more sophisticated algorithms. These algorithms primarily focus on sender reputation, engagement metrics, and authentication protocols rather than just content.
However, images still play a role, albeit often indirectly. They can impact factors that influence how an email is perceived by both automated filters and human recipients. Understanding these nuances is key to balancing visually appealing emails with strong deliverability.
Image file size and load times
One of the most significant ways images can affect deliverability is through the overall email file size. Large, unoptimized images increase the email's total size, making it slower to load and potentially triggering filters that reject oversized messages. Some email servers have strict limits, and exceeding them can lead to your email being bounced or flagged.
While an occasional large image might not immediately doom your email, consistently sending heavy emails can negatively impact your sender reputation over time. ISPs observe how recipients interact with your emails, and slow loading times can lead to frustrated users deleting messages before they fully render, contributing to lower engagement metrics.
Optimizing image file sizes is a crucial step to mitigate this risk. Compressing images, using appropriate formats (like JPG for photos and PNG for graphics with transparency), and scaling them correctly before embedding can significantly reduce email weight. Generally, it's recommended to keep individual images under 50-100KB, and the total email size under 100-200KB. More information on optimizing email sizes for deliverability can be found in our article on how email image sizes affect deliverability.
Image-to-text ratio and spam filtering
The infamous image-to-text ratio is still a topic of discussion in deliverability circles. While it's less of a rigid rule than it once was, emails composed almost entirely of images, or image-only emails, can still raise red flags with spam filters (or blocklists). Spammers often use this tactic to evade text-based content filters, making it a suspicious pattern for ISPs. This means images in emails can indeed cause them to go to spam.
A good balance between text and images is often recommended. While there's no universally agreed-upon perfect ratio, many experts suggest a 60/40 or 70/30 text-to-image ratio. This ensures that your email has enough text content for filters to analyze, reducing the likelihood of it being flagged as suspicious. Mailjet's blog on email file sizes also highlights the importance of this balance, suggesting aiming for at least a 60/40 text-to-image ratio.
Even if your email lands in the inbox, an unbalanced image-to-text ratio can affect how recipients perceive your message. Emails that appear too promotional or are difficult to read without images enabled might lead to lower engagement or, worse, spam complaints. This directly impacts your sender reputation, which is a critical factor in deliverability. Understanding how the image to text ratio affects deliverability is crucial.
User experience and engagement
Beyond technical considerations, images significantly influence user experience. Many email clients, especially in corporate settings, block images by default. If your email relies heavily on images to convey its message, recipients with blocked images will see broken links or empty spaces, leading to a poor experience.
This is where alt text becomes critical. Proper alt text provides a textual description of the image, ensuring that even if images don't load, the message remains clear and accessible. It's also vital for accessibility, allowing screen readers to describe images to visually impaired users.
A negative user experience, whether due to slow loading images or missing content, can indirectly hurt your deliverability. If recipients are consistently annoyed by your emails, they are more likely to mark them as spam, unsubscribe, or simply ignore them. These actions signal to ISPs that your emails are not valuable, which can lead to lower inbox placement over time. Our article on image-based emails and accessibility implications provides more detail.
Therefore, even if images don't directly trigger a spam filter (or blacklist) on content, their impact on user engagement and overall email health can significantly affect your long-term deliverability. Always design your emails with a graceful fallback for when images are blocked, ensuring your core message is conveyed through text.
Technical considerations and sender reputation
The way images are hosted and delivered can also have an effect on deliverability. While self-hosting images might seem appealing, using a Content Delivery Network (CDN) is generally recommended. CDNs ensure faster loading times and can reduce the burden on your own servers.
However, using a different domain for your CDN-hosted images can sometimes, in rare cases, lead to deliverability issues if that domain has a poor reputation or is blocklisted. It's generally safer if the image hosting domain is closely related to your sending domain or a reputable third-party CDN.
Ultimately, the cleanliness of your email list and your overall sender reputation are far more impactful than the presence of images. If your list is full of unengaged contacts or spam traps, images will be the least of your deliverability concerns. Beehiiv's article on email deliverability best practices states that large image files can cause deliverability issues because some email servers reject emails that are too large. A strong sender reputation allows you more flexibility in email design, including the use of images. For more on improving your overall deliverability, consider exploring our guide on why your emails are going to spam.
Balancing aesthetics and deliverability
When considering the use of images in your emails, especially for B2B audiences where images might be disabled, it is important to remember that design choices should always prioritize message clarity and deliverability. If your core audience primarily sees plain text, investing heavily in elaborate image-based designs might not yield the desired return on investment.
However, a small number of well-optimized, relevant images with descriptive alt text can enhance the user experience for those who do see them. This provides a balance between visual appeal and ensuring your message is accessible and deliverable to all recipients.
Views from the trenches
Best practices
Always include descriptive alt text for all images to ensure accessibility and convey your message even when images are blocked.
Optimize image file sizes by compressing them and using appropriate formats like JPG or PNG to reduce email load times.
Maintain a healthy image-to-text ratio, aiming for more text than images to avoid spam filter triggers, ideally 60/40 or 70/30 text to image.
Prioritize list hygiene and sender reputation above all else, as these are the primary drivers of email deliverability, regardless of image use.
Common pitfalls
Sending image-only emails, which can be a strong indicator of spam and significantly hurt deliverability.
Using very large, unoptimized image files that increase email size and can lead to emails being rejected or clipped.
Neglecting alt text, making emails unreadable and inaccessible for recipients with images blocked or using screen readers.
Assuming that images have no impact on deliverability whatsoever, ignoring the indirect effects on load times and user engagement.
Expert tips
Even if images are sometimes blocked, a few well-chosen, optimized images with good alt text can still enhance the experience for those who do see them, boosting engagement.
Consider the specific audience; B2B recipients often have images disabled by default, so ensure your core message is conveyed without them.
While direct impact is low, the indirect effects of image usage on user experience and engagement are crucial for long-term sender reputation.
Regularly monitor your email engagement metrics and spam complaint rates, as these provide the most accurate insight into your deliverability health, regardless of content.
Marketer view
Marketer from Email Geeks says that images generally do not impact email delivery, noting that many legitimate emails include images without issue.
2021-05-29 - Email Geeks
Marketer view
Marketer from Email Geeks confirms that images typically do not affect delivery as long as the email does not get clipped due to excessive size.
2021-05-30 - Email Geeks
The balanced approach to images in email
While images themselves are not inherently bad for email deliverability, their misuse can certainly lead to issues. The primary factors that influence whether an email lands in the inbox or the spam folder are more related to your sender reputation, email authentication (like SPF, DKIM, and DMARC), and recipient engagement.
To ensure your emails perform well, focus on a holistic approach that includes maintaining a clean email list, sending relevant content, securing your email sending with proper authentication, and optimizing your email content, including images. This strategy will provide the best chance for your emails to reach their intended audience.
The key is to use images strategically: to enhance your message, not to be the message itself. By following best practices for image optimization, incorporating alt text, and maintaining a healthy text-to-image ratio, you can leverage the power of visuals without compromising your email deliverability.
