Images are a powerful way to make email content visually engaging, but marketers often wonder if large images in emails increase the risk of ending up in spam folders. While images alone don’t directly trigger spam filters, certain factors—like file size, load times, and text-to-image ratio—do play a role in determining where an email ends up. This blog will explain how image size impacts deliverability, best practices for image use, and tips to ensure your emails make it to the inbox.
1. The role of image size in deliverability
Spam filters evaluate a variety of factors when deciding if an email should be flagged as spam, and image size can indirectly affect deliverability. Large images can make emails load slowly, especially on mobile devices, which can lead to a negative user experience. Additionally, emails with high image-to-text ratios, or those containing images that appear “suspicious” to spam filters, are more likely to be flagged.
Why image size matters:
- Slow loading times: Large image files take longer to load, which can frustrate recipients and increase the likelihood of being flagged by spam filters.
- High data usage: Recipients on mobile devices or slower networks may find large images data-heavy and slow, leading them to delete or mark the email as spam.
- Suspicious patterns: If your email is image-heavy with little text, it may resemble spammy or phishing emails, which often rely on large images to bypass filters.
2. Text-to-image ratio and spam filters
Emails with a high ratio of images to text are more likely to be flagged as spam. Spam filters are designed to identify emails that might be deceptive or hiding text-based spam triggers in images. An email that contains mostly images and very little text can raise red flags, making it look suspicious.
Best practices for text-to-image ratio:
- Aim for a 60:40 ratio of text to images. This ensures enough text content for filters to analyze, reducing the chance of being flagged.
- Use ALT text for all images. ALT text provides a description of each image, which improves accessibility and helps spam filters understand the image content.
- Avoid sending image-only emails with little or no text. Include a brief introduction, call-to-action, or additional text to provide context.
3. File size matters: keeping images optimized
Image file size is an important factor that can impact email deliverability. Large files increase email load times, which can lead to poor user experiences and higher spam complaints. Reducing image file size without compromising quality is key to maintaining a smooth email experience and reducing the risk of being marked as spam.
Tips for image optimization:
- Use compressed formats like JPEG or PNG for high-quality images with smaller file sizes.
- Aim to keep images under 1MB in size. Ideally, each image should be around 100–200 KB to ensure faster loading.
- Resize images to fit the email layout before uploading, rather than relying on the email platform to resize them automatically. This reduces unnecessary file size.
4. Importance of ALT text and accessibility
ALT text plays a vital role in improving accessibility and reducing the likelihood of ending up in spam. When email clients block images, ALT text gives context to recipients. Additionally, spam filters analyze ALT text to understand the content and relevance of the image, which can help improve deliverability.
How to use ALT text effectively:
- Add descriptive ALT text to every image to make it more accessible for screen readers and users with image blocking.
- Use short, relevant descriptions that explain the purpose of the image in context, avoiding overuse of keywords.
- Avoid using ALT text to “stuff” keywords, as spam filters might flag this as suspicious behavior.
5. Avoiding “Image-Only” emails
Image-only emails, which consist of a single large image or series of images without any text, are more likely to be flagged as spam. These types of emails are common in phishing scams or spam messages, as they can hide content from filters. Including meaningful text helps spam filters analyze and categorize your email more accurately.
How to create a balanced email:
- Include a combination of text and images. Even a brief introductory paragraph or a call-to-action can make a difference.
- Use clear and relevant headings and text that explains the email content rather than relying solely on images.
- Ensure that critical information, like offers or CTAs, is included in text form rather than exclusively within images.
6. Monitor engagement and deliverability metrics
Understanding your email performance metrics, such as open rates, bounce rates, and spam complaints, can help you identify if large images or image-heavy designs are affecting deliverability. Monitoring engagement gives insight into how your audience responds and allows you to adjust accordingly.
Key metrics to monitor:
- Open rates: Low open rates could indicate that spam filters are affecting your deliverability.
- Click-through rates (CTR): If CTR drops, it might indicate issues with load times or overall content relevance.
- Spam complaints and unsubscribes: Higher rates of spam complaints or unsubscribes can signal issues with email quality, which may be impacted by image use.
7. Consider mobile and network limitations
Many recipients open emails on mobile devices or in environments with limited data, where large images may not load properly or take too long to display. Optimizing images for mobile viewing improves accessibility, reduces frustration, and decreases the likelihood of spam complaints.
Tips for mobile-friendly images:
- Use responsive design to ensure images adjust to different screen sizes.
- Avoid large header images that may not display well on mobile screens.
- Prioritize vertical layouts over horizontal ones for better mobile readability.
Conclusion
Large images can indirectly increase the chances of an email being flagged as spam, especially if they lead to slow load times, create a high image-to-text ratio, or are part of an image-only email. To keep your emails out of spam folders, focus on creating a balanced mix of text and images, optimize image file sizes, and use ALT text for accessibility. By following these best practices, you can create visually engaging emails that deliver value without compromising deliverability.