What are the negative impacts of using large images in email marketing and how to fix them?

Key findings

• Load time impacts: Excessively large images significantly increase the time it takes for an email to load, leading to recipient frustration and potential abandonment.
• User experience degradation: Recipients, particularly those on mobile devices with limited data or slower connections, may abandon emails that take too long to render.
• Deliverability risks: Some mailbox providers may reject messages exceeding certain size limits, especially if images are embedded directly, impacting your ability to reach the inbox. Mailjet suggests that large images can impact email load time, resulting in your subscribers deleting your email before it has been downloaded, which hurts overall deliverability.
• Engagement metrics decline: High load times can lead to lower open rates (even if partially due to non-loading emails), reduced click-through rates, and ultimately, lower conversion rates.
• Storage and bandwidth: Embedded images add to the total message size, consuming recipient mailbox space and increasing bandwidth costs for senders.

Key considerations

• Optimize image sizes: Always compress and resize images to the smallest possible file size without sacrificing visual quality, ensuring they are appropriate for email display. This aligns with best practices for image file sizes.
• Link, don't embed: Generally, host images on a server and link to them using the <monospace>src</monospace> attribute in HTML. This prevents the image size from counting towards the email's total message size.
• Monitor email performance: Regularly check your email metrics for low open rates or high unsubscribe rates, which can be indicators of poor image optimization.
• Educate content creators: Ensure anyone adding images to email templates understands the impact of large files and adheres to optimization guidelines.

Key opinions

• Engagement killers: Large images lead to long load times, which directly translate into low engagement, open rates, and conversions because subscribers won't wait. For example, Tower Marketing highlights that image-heavy emails greatly increase load time, which is detrimental to user engagement.
• Unsubscribe risk: If emails are consistently slow to load or consume excessive data, recipients are likely to unsubscribe.
• Impact on metrics: While open rates aren't perfect, a drastic drop due to large images can still alarm designers and marketers, signaling a problem with user experience.
• Data consumption: Sending massive files is inconsiderate to users with limited mobile data plans, potentially damaging sender reputation.

Key considerations

• Pre-send QA: Implement robust quality assurance processes to catch oversized images before campaigns are sent.
• Image hosting strategy: Always use externally hosted images (referenced by URL) rather than embedding them directly into the email HTML to keep message size small. This is especially important for image-only emails.
• User experience focus: Prioritize fast loading and accessibility for all recipients over excessively high-resolution visuals that don't add significant value.
• Cost implications: Be aware that sending massive files can incur significant bandwidth costs, especially for large lists.

Key opinions

• Message size limits: Some mailbox providers may reject messages that exceed a certain total size, especially if images are embedded, potentially leading to bounces.
• Data plan impact: Very large images are particularly problematic for recipients with limited mobile data plans, as they consume significant bandwidth and can lead to frustration or non-engagement.
• User experience priority: It's considered absurd to ask users to download and store excessively large images that don't offer substantial value, as it negatively impacts their experience and device storage.
• Loading performance: Slow loading times, even for linked images, result in poor user experience and can influence how often future emails are opened. The Kickbox Blog notes that excessive high-resolution images increase load time and detract from effectiveness.

Key considerations

• Embedded vs. linked distinction: While less common in marketing emails, embedded images contribute directly to message size, making it a critical factor for rejection, whereas linked images primarily affect download time.
• Proactive image optimization: Ensure images are properly resized and compressed before they are even uploaded or linked, to minimize their impact on both message size and load time. This also ties into improving deliverability for large emails.
• Caching mechanisms: Understand that once a corrected (smaller) image replaces an oversized one at the same URL, recipients will download the smaller version due to caching or CDN updates.
• Holistic email design: Design emails with both visual appeal and technical efficiency in mind, recognizing that image size is a critical component of overall email health and performance.

Key findings

• Slow load times: Large or unoptimized images are a primary cause of slow email loading, directly impacting recipient engagement. As VerticalResponse documentation suggests, they can negatively impact deliverability.
• Decreased engagement: Recipients are likely to delete or abandon emails that take too long to download, leading to reduced open and click-through rates.
• Deliverability issues: Many email clients and spam filters may flag or even block excessively large or image-heavy emails, affecting inbox placement.
• Resource consumption: Large image files consume more bandwidth for both sender and recipient, and embedded images take up valuable mailbox storage.

Key considerations

• Optimize for web: Images should be optimized for web use, meaning they are compressed and saved at appropriate resolutions and dimensions for email display, typically under 100-200KB for most email images.
• Use proper formats: Choose efficient image formats (e.g., JPEG for photos, PNG for graphics with transparency) to minimize file size.
• HTML and CSS best practices: Utilize HTML and CSS to control image display dimensions, rather than relying on a large source image scaled down. This also applies to understanding how email code quality and size impact deliverability.
• Alt text implementation: Always include descriptive alt text for images to ensure accessibility and provide context even if images are blocked or slow to load.