Why is my email template getting higher open rates in Gmail?
Matthew Whittaker
Co-founder & CTO, Suped
Published 26 Apr 2025
Updated 19 Aug 2025
7 min read
Discovering why one email template performs significantly better than another in terms of open rates, especially within an inbox like Gmail, can be a puzzling experience. I've encountered many scenarios where seemingly minor differences lead to substantial shifts in engagement metrics. It's not always about the subject line or the sending time, but often involves the underlying technical structure of the email itself, or how the mailbox provider handles it.
When one template sees a dramatically higher open rate (perhaps even a 95% increase, as I've seen in some cases) while others lag, it signals something more fundamental than simple content preference. It suggests that factors beyond what's immediately visible to the sender are at play, influencing where the email lands and how it's perceived by Gmail's algorithms.
The key to uncovering these discrepancies lies in a methodical investigation of technical elements, Gmail's unique inbox categorization, and the integrity of your testing methodology. I'll share insights into how to diagnose and understand these significant differences in open rates.
The true meaning of open rates
Open rates are a foundational metric in email marketing, but their reliability has been debated, especially with changes in how various email clients track them. Gmail, for instance, often pre-fetches images, which can sometimes lead to inflated open rates, particularly for emails that land in the primary inbox. This means an email might be 'opened' technically, but not necessarily viewed by the recipient.
When analyzing open rate disparities between templates, I always recommend looking closely at the click-through rate (CTR) as well. If a template has a very high open rate but a comparatively low CTR, it could indicate that the 'opens' are more technical (e.g., image pre-fetching) rather than genuine user engagement. This discrepancy suggests that while the email might be reaching the inbox, its content isn't compelling enough to drive interaction.
I’ve often found that discrepancies between open rates and click rates can signal underlying issues with data capture or even how the email client processes the message. Some experts suggest that looking at open rates alone can be unreliable, and that other metrics are more important now. For more details on this, see why open rates are becoming less reliable. If one template is getting a much higher open rate, but the CTR isn't proportionally higher, it could be a false positive masking a deliverability issue with the lower-performing template, or simply an artifact of Gmail's rendering.
Metric
Control Template (Lower Open Rate)
Test Template (Higher Open Rate)
Open rate
12.45%
24.45%
Click/open rate
8.96%
6.15%
Raw CTR (based on deliveries)
1.12%
1.49%
Decoding template code differences
Even with similar file sizes, the underlying HTML and CSS structure of your email templates can significantly influence deliverability and rendering. Small differences in how images are loaded, links are formatted, or even specific characters used can impact how Gmail processes and displays your email. I've seen cases where seemingly innocuous elements cause issues.
One common issue is Gmail clipping. While the stated limit is around 102KB, I've observed that other factors beyond just size, such as errant characters or complex HTML, can also trigger clipping. When an email clips, the recipient sees only a portion of it, with a 'View entire message' link. This can severely depress open rates because the tracking pixel, usually at the bottom, might not load.
Differences in background color support or other CSS properties between templates can also indicate underlying HTML validation issues. If a template isn't rendering correctly in your own Gmail, it's a strong indicator that similar problems might be affecting other recipients, potentially leading to lower engagement and opens. This is often why new email templates can affect deliverability.
Problematic template example
A common cause of unexpected rendering or deliverability issues is malformed HTML or the presence of hidden, non-standard characters. These can lead to Gmail clipping the email or rendering it incorrectly, which directly impacts the user experience and open rate.
Example of problematic HTML snippethtml
<!DOCTYPE html><html><body><!-- Extremely long and non-standard comment that might trigger clipping --> <img src="https://example.com/tracking-pixel.gif" width="1" height="1"> <style>body { background-color: #ff0000; }</style> <a href="https://untrusted-domain.com">Click here</a> <!-- This background color might not be supported in Gmail for the body tag directly, leading to rendering inconsistencies. --> </body></html>
Gmail's inbox categorization
Gmail employs a sophisticated algorithm to categorize incoming emails into various tabs: Primary, Social, Promotions, and Updates. Where your email lands significantly influences its visibility and, consequently, its open rate. A template that consistently lands in the Primary tab will naturally exhibit higher open rates than one relegated to the Promotions tab, simply because users are more likely to see and interact with emails in their main inbox.
I've observed that small changes in template design or content can shift an email's tab placement. For instance, emails with too many images, promotional language, or certain types of links can be classified as 'Promotions'. While this isn't necessarily a spam classification, it significantly reduces visibility, as many users don't actively check their Promotions tab. This can explain why Gmail open rates are lower when emails land in these other tabs.
Furthermore, Gmail's pre-fetching of images, as mentioned earlier, is more prevalent in the Primary inbox. If one template consistently achieves primary inbox placement, its open rate might appear higher due to these automatic image loads, even without direct user interaction. This highlights the importance of not solely relying on open rates as a measure of engagement within Gmail.
Inbox tab impact
Gmail's tabbed inbox system directly influences email visibility. An email landing in the Primary tab receives immediate attention, while emails in Promotions or Updates tabs often go unnoticed or are checked less frequently.
Primary tab: High visibility, more likely to be genuinely opened and interacted with. Also more prone to image pre-fetching.
Promotions tab: Lower visibility, often checked only periodically by users. Open rates can appear lower despite successful delivery.
Strategic testing and analysis
To truly understand why one template performs better, I advocate for a rigorous testing methodology. This includes ensuring your A/B tests are conducted on genuinely random subsets of your audience and that you're accumulating sufficient data over a prolonged period. A test running for only a few days with limited recipients might not provide a stable or representative picture.
When reviewing results, I always segment the analytics by domain. If the significant open rate difference is observed exclusively in Gmail, it points to Gmail-specific factors rather than a universal issue with the template. If other ISPs show similar patterns, the problem might be more broadly related to sender reputation or content, requiring a different approach.
It's also beneficial to use email rendering testing tools to preview how your templates appear across various email clients and devices. These tools can highlight subtle HTML or CSS issues that might not be immediately apparent in your own inbox but could be affecting broader deliverability or user experience. Remember, consistent testing and detailed analysis are paramount to improving your Gmail open rates.
A/B testing pitfalls
Insufficient data: Running tests on small audience segments can yield statistically insignificant results.
Short duration: Ending tests too soon might miss delayed engagement or cyclical patterns.
No randomization: Not splitting segments randomly can introduce bias into your test results.
Effective testing practices
A/B test systematically: Randomize and split your audience to ensure reliable comparisons.
Monitor beyond open rates: Include CTR, conversions, and unsubscribe rates in your analysis.
Segment by ISP: Identify if the issue is specific to Gmail or applies across providers.
Views from the trenches
Best practices
Always run A/B tests on random, large subsets of your audience to ensure statistical significance.
Segment your email analytics by email service provider to pinpoint if issues are Gmail-specific or broader.
Prioritize email authentication like SPF, DKIM, and DMARC for strong sender reputation and better inbox placement.
Regularly test email templates for HTML errors, clipping, and rendering inconsistencies across different clients.
Common pitfalls
Misinterpreting high open rates solely as engagement, especially when CTR is disproportionately low.
Failing to account for Gmail’s tabbed inbox (Promotions vs. Primary) when analyzing open rates.
Ignoring the impact of subtle HTML/CSS differences or errant characters on email clipping.
Not having enough data volume or testing duration to draw reliable conclusions from email experiments.
Expert tips
Implement BIMI (Brand Indicators for Message Identification) to enhance brand visibility and trust in Gmail and other supporting clients.
Monitor Google Postmaster Tools for detailed insights into your Gmail sender reputation, spam rates, and delivery errors.
Clean your email lists regularly to remove inactive or problematic addresses, which can improve overall engagement.
Keep email content concise and directly relevant to avoid triggering spam filters or tab reclassification.
Expert view
Expert from Email Geeks says to begin by thoroughly reviewing your testing methodology. Confirm if the A/B testing is on a random subset and being done consistently, as this foundation is critical for valid insights.
2021-02-17 - Email Geeks
Expert view
Expert from Email Geeks says that if a genuine difference between templates is confirmed, then investigate the hostnames used in links and image tags to check for any red flags that might lead to spam folder placement.
2021-02-17 - Email Geeks
Unlocking template performance
Unraveling why one email template gets significantly higher open rates in Gmail than another requires a holistic approach. It's rarely a single factor, but rather a combination of how Gmail's algorithms interpret your template's technical structure, its content, and its impact on inbox placement.
I encourage you to look beyond raw open rates and consider companion metrics like click-through rates, and to scrutinize your template's HTML for potential clipping issues or rendering inconsistencies. Understanding Gmail's tab categorization and how your templates interact with it is also paramount. By methodically investigating these areas, you can gain a clearer picture of your email performance and optimize your campaigns for genuine engagement.
