How do email image sizes affect deliverability and Gmail promotions tab placement?
Michael Ko
Co-founder & CEO, Suped
Published 10 Jul 2025
Updated 19 Aug 2025
8 min read
The size of images in your emails can feel like a puzzling variable. You want your emails to be visually engaging and attractive, but you also worry about whether large images might cause deliverability issues or push your messages into Gmail's Promotions tab. It's a common concern among email marketers and deliverability professionals.
The truth is, the impact isn't always direct, but it's definitely there. Mailbox providers, including Gmail, consider various factors when deciding where to place an email, and how images are handled is part of that complex equation. It's not just about the kilobytes; it's also about user experience and content signals.
Let's explore how email image sizes specifically affect whether your messages land in the inbox or the Promotions tab, and what you can do to optimize your campaigns for better results.
The direct impact of email image size on deliverability
While an excessively large email file size can sometimes indirectly affect deliverability, it's not typically a primary reason for emails going to spam filters in the way, for example, a bad sender reputation might be. The main concern with large images is how they affect email load times. If an email takes too long to load, recipients might abandon it, leading to lower engagement rates.
This reduced engagement can then signal to mailbox providers that your emails are not valuable, potentially impacting your sender reputation over time. Industry standards generally recommend keeping the overall email size, including all images and HTML, to a maximum of around 100KB. This ensures a swift loading experience for most users, even those with slower internet connections or on mobile devices.
It's also important to distinguish between the size of individual images and the overall email content. While a single large image might contribute to a heavy email, it's the cumulative size and the image-to-text ratio that can draw attention. For instance, emails that consist almost entirely of images may trigger spam filters because they could be an attempt to hide malicious content or evade text-based content analysis. To avoid such issues, ensure you protect deliverability for image-only emails.
Gmail's promotions tab and image content
Gmail's Promotions tab is designed to help users organize their inboxes. It aggregates marketing and promotional emails, allowing recipients to view them when they are ready to engage with commercial content. From a user experience perspective, this can be beneficial, as it reduces clutter in the primary inbox.
When it comes to image usage, Gmail's algorithm looks at the email's overall intent and content signals rather than just the image file size. Emails that are heavily designed with large banners, product carousels, or prominent calls to action (CTAs) are more likely to be classified as promotional. This classification is based on the *nature* of the content, not solely on how many kilobytes the images occupy.
Therefore, if your email primarily consists of eye-catching visuals and direct marketing messages, it's very probable it will land in the Promotions tab. This isn't necessarily a negative outcome, as many recipients actively check this tab for deals and updates. However, if your goal is to land in the Primary inbox, you'll need to focus on content balance and reduce the overt promotional signals. Understanding Gmail's tab impact is key.
An email that features an image carousel feature for showcasing multiple products is a classic example of content that will likely be categorized as promotional.
Promotional signals
Image-to-text ratio: Emails with a high density of images relative to text are often flagged as promotional.
Design elements: The presence of large banners, product listings, or pricing information suggests a marketing message.
Link density: Numerous links, especially to e-commerce pages, are a strong indicator of promotional content.
Optimizing images for deliverability and inbox placement
Optimizing your images is crucial for maintaining good deliverability and influencing Gmail tab placement. The goal is to reduce file size without compromising visual quality. This involves several key practices:
Image compression: Always compress your images before uploading them to your email service provider. Many tools are available that can significantly reduce file size while retaining visual fidelity. This ensures faster load times for recipients.
Appropriate file formats: Use JPG for photographs, PNG for images with transparency or sharp edges, and GIF for animated content. Each format has its strengths and weaknesses regarding file size and quality. For more details, consult best practices for image files.
Responsive design: Ensure your email template and images are responsive. This means they should automatically adjust to fit various screen sizes, from desktops to mobile phones. This improves the user experience and can positively influence engagement metrics.
Beyond size, the image-to-text ratio plays a significant role in how mailbox providers perceive your email. While not as problematic as in the past, heavily image-based emails can still be flagged as spam if they lack sufficient text content. A good balance provides context for spam filters and ensures your message is readable even if images are blocked or fail to load.
Always use alt text (alternative text) for all your images. This descriptive text displays if an image doesn't load and is crucial for accessibility. It also provides valuable context to mailbox providers about the image content, reducing the chances of misclassification. This helps improve overall email deliverability.
Holistic deliverability and image considerations
While image size and content are important, they are just one piece of the broader email deliverability puzzle. Your sender reputation, email authentication, and overall engagement metrics play a much larger role in whether your emails reach the inbox or are flagged as spam.
Maintaining a strong sender reputation is paramount. This means consistently sending wanted mail, avoiding spam traps, and keeping your complaint rates low. Even with perfectly optimized images, a poor sender reputation will lead to emails being blocked or placed in the spam folder. Regularly monitor your sender score and address any issues promptly. It's also important to avoid being listed on an email blacklist (or blocklist).
Email authentication protocols like SPF, DKIM, and DMARC are fundamental to deliverability. These records verify that your emails are legitimately from your domain, preventing spoofing and improving trust with mailbox providers. Correct authentication signals legitimacy, regardless of your email's image content or size.
Finally, regularly conducting email deliverability tests is essential. These tests can reveal how your emails perform across different providers and identify potential issues, including those related to image rendering, overall email size, and content classification. This proactive approach helps you address problems before they significantly impact your campaigns.
Views from the trenches
Best practices
Regularly test your email campaigns using a seedlist tool to see how images affect placement.
Balance your email content with a healthy image-to-text ratio to avoid spam filters.
Utilize a content analysis tool to check for potential flags related to overall email size and images.
Common pitfalls
Overlooking slow email load times caused by unoptimized images, which hurts engagement.
Misinterpreting Gmail's Promotions tab as a spam folder, it's often the intended destination.
Expert tips
Focus on the total message size, not just individual image sizes, as some filters consider the whole payload.
Prioritize user experience and avoid content that feels like an interruption to prevent spam complaints.
Ensure images are responsive and scale correctly on all devices to improve readability and engagement.
Expert view
Expert from Email Geeks says there is no specific hard and fast rule for email image sizes affecting deliverability, and the best approach is to test using a seedlist tool.
2023-05-10 - Email Geeks
Expert view
Expert from Email Geeks says that emails are typically categorized into the Promotions folder if they are promotional in nature. This can be beneficial because recipients are often overwhelmed with notifications, and a reputation for sending irrelevant interruptions quickly leads to spam complaints.
2023-05-11 - Email Geeks
Summary and best practices
Ultimately, while email image size isn't a direct trigger for spam filters as much as other factors, its indirect effects on load times and user experience are significant. Additionally, the type and volume of images in your emails strongly influence whether Gmail classifies them as promotional.
To ensure your emails perform optimally, focus on a multi-faceted approach. Optimize your images for web and mobile, paying attention to both file size and visual composition. Strive for a balanced image-to-text ratio and use descriptive alt text.
By combining these image best practices with robust email authentication, a strong sender reputation, and consistent testing, you can significantly improve your email deliverability and achieve your desired inbox placement, whether it's the Primary or Promotions tab.
Gmail, consider various factors when deciding where to place an email, and how images are handled is part of that complex equation. It's not just about the kilobytes; it's also about user experience and content signals.
Gmail classifies them as promotional.
