Why are my email open rates low when using images in my email template?
Michael Ko
Co-founder & CEO, Suped
Published 31 Jul 2025
Updated 18 Aug 2025
7 min read
It can be perplexing when your email open rates drop, especially after implementing a new template with more images. You might immediately suspect that the images are causing your emails to get stuck or sent to spam folders, but the reality is often more complex. While images do play a role in email deliverability and how open rates are tracked, they are rarely the sole culprit for a sudden decline.
Email deliverability is a multifaceted challenge, and many factors contribute to whether your message lands in the inbox or gets diverted. When images are part of the equation, it introduces additional considerations, from how email clients render your content to how internet service providers (ISPs) perceive your email's authenticity and intent. My goal here is to help you understand these dynamics and provide actionable steps to diagnose and address any issues.
Let's explore why using images in your email template might lead to lower reported open rates and what steps you can take to ensure your messages not only reach the inbox but also engage your audience effectively.
The illusion of low open rates
One of the most common misunderstandings about images and email open rates stems from how open rates are actually measured. Most email service providers (ESPs) track opens by embedding a tiny, invisible 1x1 pixel image within the email. When a recipient opens the email and their email client downloads this pixel, it registers an open.
However, this method is not foolproof. Many email clients, especially desktop clients, block images by default for security and privacy reasons. If images are blocked, the tracking pixel won't load, and the open will not be recorded, even if the user reads the email content. This can significantly deflate your reported open rates, creating the illusion of a deliverability problem when emails are, in fact, reaching the inbox.
Furthermore, newer privacy features, such as Apple Mail Privacy Protection, can artificially inflate open rates by preloading images, including tracking pixels, before a user even views the message. This means open rates are becoming an increasingly unreliable metric for true engagement. Focusing on other metrics like click-through rates (CTR) and conversions can provide a more accurate picture of your campaign performance, as highlighted in this article about why open rates are dying.
Understanding open rate tracking
Email open rates are calculated based on the download of a small, invisible pixel. If images are not loaded by default or are explicitly blocked by the recipient, this pixel will not fire, leading to an unregistered open.
Privacy settings: Many email clients have default settings that prevent images from loading automatically, requiring user action to display them. This directly impacts open tracking.
Email clipping: If your new template is very long or contains a lot of HTML, email clients like Gmail might clip the message, hiding the open tracking pixel at the bottom. This means the email is delivered, but the open isn't recorded.
Inaccurate metrics: Given these factors, open rates should not be your sole KPI for email campaign success. Consider how all-image emails can influence open rates and whether they are truly reliable for gauging engagement.
Image usage and its impact on deliverability
While images might not directly lead to emails being blocked by filters, their improper use can signal spam-like behavior to ISPs, impacting your sender reputation and actual deliverability. A template dominated by images with little text is a common red flag.
Spam filters often analyze the text-to-image ratio. Emails that are primarily images can be seen as an attempt to bypass text-based spam detection. This is because spammers sometimes embed malicious links or suspicious content within images to avoid detection. For optimal deliverability, a balanced 60-40 text-to-image ratio is often recommended, or even higher text content for cold outreach.
Additionally, large image file sizes can negatively affect loading times, leading to a poor user experience. If an email takes too long to load, recipients might abandon it before it fully renders, or even mark it as spam, indirectly hurting your reputation. This is why images can indeed affect deliverability. Maintaining a healthy text-to-image ratio and optimizing image sizes are crucial for ensuring your emails land in the inbox and are well-received.
Image-heavy template pitfalls
Spam filter triggers: Emails with a high image-to-text ratio can appear suspicious to spam filters, potentially leading to increased spam classifications. This is a key reason why image-only emails are often bad for deliverability.
Slow loading times: Large image files can make your email slow to load, frustrating recipients and increasing the likelihood of them closing the email before it fully renders or even marking it as spam due to perceived poor quality.
Accessibility issues: Screen readers and users with images disabled will miss critical information if your email relies solely on images for content.
Best practices for images in emails
Optimize image sizes: Compress images to reduce file size without sacrificing quality. This improves loading times and overall user experience.
Maintain text-to-image balance: Aim for a ratio that prioritizes text content, ensuring your message is clear even if images don't load. Avoid single large images that replace all text content.
Use alt text: Always include descriptive alt text for all images. This ensures your message is conveyed even when images are blocked and improves accessibility.
Responsive design: Ensure your email templates and images are responsive and display correctly on various devices and screen sizes.
Here's an example of how to include an image with proper alt text and a responsive width in your email HTML, ensuring it adapts to different screen sizes and provides a fallback for image blocking:
Optimized image HTML for emailhtml
<img src="https://example.com/image.jpg" alt="Descriptive text for the image content" style="max-width: 100%; height: auto; display: block;" />
Diagnosing and mitigating image-related open rate issues
When you observe low open rates with a new template, it's crucial to differentiate between an actual deliverability issue and an inaccurate open rate reporting problem. The first step is to check if any specific mailbox provider is showing disproportionately lower opens than others.
If, for example, your Gmail open rates are notably low, utilizing Google Postmaster Tools can provide valuable insights into your domain and IP reputation, spam rates, and delivery errors directly from Google's perspective. If your Postmaster Tools dashboard shows a healthy reputation, the issue might be related to open tracking rather than direct blocking.
It's also essential to inspect your overall email engagement metrics, not just open rates. Look at your bounce rates, complaint rates, and unsubscribe rates. If these metrics remain stable or are not increasing significantly, your email reputation might not be severely impacted, even with a lower reported open rate. However, if these metrics are worsening, it signals a broader deliverability challenge, perhaps leading to your emails going to spam.
Continuing to send an email campaign with a low initial open rate, especially if coupled with rising complaint or bounce rates, can indeed harm your sender reputation over time. ISPs use user engagement and complaint data to assess your trustworthiness. If your messages consistently receive low engagement or high complaints, your domain could end up on a blacklist (or blocklist), or face increased filtering. This reinforces the importance of monitoring metrics beyond just open rates and proactively addressing any red flags to improve email deliverability rates.
Issue Category
Symptom
Action to Take
Open tracking inaccuracy
Low reported opens, but other metrics (clicks, conversions) are stable. Postmaster Tools shows good reputation.
Check if email clients are blocking images or if the email is clipping (tracking pixel not loaded). Focus on engagement metrics like CTR.
Content quality/ratio
High image-to-text ratio, large image file sizes, slow loading times observed during testing.
Optimize images (compress, use alt text), balance text and images, ensure responsive design.
Sender reputation decline
Low open rates coupled with rising bounces, complaints, or unsubscribes. Postmaster Tools shows reputation warning.
Clean your email list, improve content relevance, segment audiences, verify email authentication (SPF, DKIM, DMARC), and consider your email blacklist status.
Optimizing for both engagement and deliverability
Addressing low email open rates, especially when using image-heavy templates, requires a holistic approach. It's often not just about the images themselves, but how they interact with email client rendering, user preferences, and spam filters. A crucial step is verifying your open tracking pixel is actually loading correctly. Sometimes, an ESP might experience an outage, or the pixel's URL might be using HTTP instead of HTTPS, preventing it from loading in some clients.
Beyond technical checks, focus on fundamental email marketing best practices. Maintain a clean email list by regularly removing inactive or invalid addresses, as a high number of unengaged recipients will naturally depress your open rates and signal low engagement to ISPs. Segment your audience to send more relevant content, which in turn boosts engagement. Remember, consistent positive engagement is your best defense against deliverability issues and reputation damage. You can read more about why your email open rates drop suddenly.
Ultimately, your email template design should support your message and deliverability goals. Balance compelling visuals with sufficient text, optimize image sizes, and always use alt text. By combining careful template design with diligent monitoring of your email metrics and sender reputation, you can ensure your emails consistently reach your audience and achieve the desired results, even with image-rich content.
Views from the trenches
Best practices
Balance images with sufficient text to maintain a healthy text-to-image ratio and avoid spam filter triggers.
Always include descriptive alt text for images to ensure accessibility and content understanding, even when images are blocked.
Compress and optimize all images to reduce file size, which improves email loading times and user experience.
Regularly monitor overall email metrics, including bounces, complaints, and unsubscribes, not just open rates, for a comprehensive view of deliverability.
Common pitfalls
Using a template that is almost entirely images can trigger spam filters and lead to poor deliverability.
Failing to optimize image sizes, resulting in slow loading emails that recipients might abandon or mark as spam.
Relying solely on open rates as a key performance indicator, as they can be inaccurate due to image blocking or privacy features.
Ignoring other critical metrics like bounce rates and complaint rates when diagnosing deliverability issues.
Expert tips
Sender reputation is built on user behavior, so focus on content that drives engagement rather than just avoiding image-related pitfalls.
Analyze disproportionately lower open rates from specific mailbox providers, as this can indicate targeted filtering issues.
Be aware of privacy changes (e.g., Apple Mail Privacy Protection) that can skew open rate data; adapt your measurement strategy accordingly.
Periodically check your email templates for unclosed tags or formatting errors that could affect the loading of tracking pixels.
Expert view
Expert from Email Geeks says that additional images alone are unlikely to cause significant filtering. Filters primarily respond to user behavior, so focus on how recipients interact with your messages.
January 5, 2021 - Email Geeks
Expert view
Expert from Email Geeks suggests that a low open rate might be due to non-filtering factors like recipient apathy, holidays, or full inboxes, and that a single campaign's lower-than-usual open rate shouldn't be overreacted to. It's important to look at holistic metrics before concluding there's a problem.
Gmail might clip the message, hiding the open tracking pixel at the bottom. This means the email is delivered, but the open isn't recorded.
Gmail open rates are notably low, utilizing Google Postmaster Tools can provide valuable insights into your domain and IP reputation, spam rates, and delivery errors directly from Google's perspective. If your Postmaster Tools dashboard shows a healthy reputation, the issue might be related to open tracking rather than direct blocking.
