Why did my email have lower open rates in Gmail, and go to spam?
Michael Ko
Co-founder & CEO, Suped
Published 5 Jun 2025
Updated 15 Aug 2025
6 min read
Discovering that your carefully crafted emails are ending up with lower open rates in Gmail or, worse, landing directly in the spam folder, can be incredibly frustrating. It's a common issue that many email marketers and businesses face, especially given the evolving and increasingly stringent filters employed by major mailbox providers. The challenge often lies in understanding that there isn't a single, straightforward cause but rather a complex interplay of factors.
While a low open rate or a high spam placement for a single email might seem like an isolated incident, it can signal deeper underlying issues with your email program. It's crucial to look beyond immediate symptoms and investigate the broader context of your sending practices and sender reputation. This guide will help you understand why your Gmail open rates might be low and what causes emails to be classified as spam.
Understanding Gmail's email filtering
One of the first things to understand is that Gmail's spam filtering system is incredibly sophisticated and dynamic. It doesn't rely on a simple checklist of spam trigger words or isolated issues like a single link or a specific subject line. Instead, it uses a complex algorithm that considers hundreds of variables, many of which are personalized to each recipient. This means an email that lands in the inbox for one person might go to spam for another, even from the same sender.
This complexity means that diagnosing why a specific email had a lower open rate or went to spam can be challenging. It's rarely about one obvious element. For example, a subject line like "Open this email + save nature" might not inherently trigger spam filters on its own, but combined with other factors, it could contribute to an overall negative signal. The algorithm weighs different factors based on context and user behavior.
Another common misconception is equating landing in the Promotions tab with going to spam. While emails in the Promotions tab typically see lower open rates compared to the primary inbox (sometimes a 10-15% drop), they are still delivered. An email going to the spam folder, however, often means an open rate close to zero. It's important to distinguish between the two for accurate diagnostics.
Gmail's filtering system
The filtering system is sophisticated, using hundreds of variables to determine inbox placement. This includes past engagement, content relevance, sender reputation, and personalization. A single email's performance is often a reflection of these combined factors rather than one specific element.
Factors impacting email deliverability and open rates
When your emails go to spam, it directly impacts open rates because recipients never see them. A critical component that influences whether your emails land in the inbox or the spam folder is your sender reputation. Gmail heavily relies on this to determine trust. A poor reputation signals to mailbox providers (MBPs) that your emails might be unwanted, leading to stricter filtering or outright blocking (blocklisting).
Your sender reputation is influenced by various factors. Engagement metrics, like open rates and click-through rates, play a significant role. If your subscribers consistently don't open or click your emails, it indicates to Gmail that your content might not be relevant or desired by your audience. This can negatively impact your sender reputation, making it more likely for future emails to go to spam or the Promotions tab. Conversely, high engagement strengthens your reputation.
Another critical element is email authentication. SPF, DKIM, and DMARC are essential for proving to Gmail that your emails are legitimate and not spoofed. Without proper authentication, even well-intentioned emails can be flagged as suspicious and sent to spam. Google's sender guidelines explicitly emphasize the importance of these records.
Sender reputation
High engagement: Consistent opens and clicks signal a healthy mailing list and relevant content to Gmail.
Low complaint rates: Few recipients marking your emails as spam improves your standing.
Valid authentication: Proper SPF, DKIM, and DMARC records build trust with Gmail's filters.
Personalized content: Tailoring emails to individual interests increases engagement.
Clean list hygiene: Regularly removing inactive subscribers and spam traps prevents reputation damage.
Diagnosing issues and troubleshooting
If you've noticed a sudden drop in Gmail open rates or an increase in spam placements, the first step is to avoid panicking over a single send. Sometimes, it can be a blip. However, if you see a consistent pattern across multiple sends, or a significant, sudden shift in placement, it's time to investigate. Monitoring your metrics regularly by internet service provider (ISP) or email service provider (ESP) is crucial for identifying these patterns.
Using Google Postmaster Tools can provide valuable insights into your domain and IP reputation with Gmail, spam rates, and authentication errors. This data is far more reliable than relying solely on open rates, especially since Apple's Mail Privacy Protection has made open rate tracking less accurate. Pay close attention to trends in your sender reputation and spam complaint rates.
If you identify a significant issue, it may be necessary to reassess your email strategy. This could involve cleaning your subscriber list of inactive users, segmenting your audience more effectively, improving your email content to boost engagement, or reviewing your email sending infrastructure to ensure proper authentication is in place. Consistent, positive engagement signals are key to building and maintaining a strong sender reputation with Gmail (and other providers) over time.
Factor
Impact on deliverability
Action to take
Low engagement
Signals to Gmail that emails are unwanted, leading to spam folder placement and lower open rates.
Emails lack verification, increasing the likelihood of being marked as spam or blocked.
Ensure SPF, DKIM, and DMARC are correctly set up and aligned.
High complaint rate
Directly harms sender reputation, leading to stricter filtering.
Provide clear unsubscribe options, send relevant emails, and manage list expectations.
Views from the trenches
Best practices
Maintain a clean and engaged email list by regularly removing inactive subscribers.
Always ensure your emails are properly authenticated with SPF, DKIM, and DMARC records.
Monitor your sender reputation and deliverability metrics using tools like Google Postmaster Tools.
Common pitfalls
Sending emails to unengaged or inactive subscribers, which can harm sender reputation.
Ignoring authentication protocols like SPF, DKIM, and DMARC.
Making assumptions about a single email's performance without looking for patterns.
Expert tips
Gmail's spam filtering is highly dynamic and personalized; a single element rarely causes a spam classification.
A drop in open rates may mean emails are landing in the Promotions tab rather than the spam folder.
Focus on holistic email program health rather than isolated metrics for long-term deliverability success.
Expert view
Expert from Email Geeks says
2020-12-08 - Email Geeks
Marketer view
Marketer from Email Geeks says it is confusing when open rates drop for engaged subscribers but increase for a broader list, making diagnostics difficult.
2020-12-08 - Email Geeks
Building long-term deliverability success
Dealing with lower open rates and emails going to spam in Gmail is a multi-faceted challenge that requires a comprehensive approach. It's not just about tweaking a subject line or avoiding certain keywords, but rather nurturing your overall sender reputation and consistently demonstrating to Gmail that your emails are valued by your recipients.
By focusing on strong email authentication, maintaining a clean and engaged subscriber list, providing relevant and personalized content, and diligently monitoring your deliverability metrics, you can significantly improve your Gmail inbox placement and boost your open rates.
Gmail or, worse, landing directly in the spam folder, can be incredibly frustrating. It's a common issue that many email marketers and businesses face, especially given the evolving and increasingly stringent filters employed by major mailbox providers. The challenge often lies in understanding that there isn't a single, straightforward cause but rather a complex interplay of factors.
Gmail's spam filtering system is incredibly sophisticated and dynamic. It doesn't rely on a simple checklist of spam trigger words or isolated issues like a single link or a specific subject line. Instead, it uses a complex algorithm that considers hundreds of variables, many of which are personalized to each recipient. This means an email that lands in the inbox for one person might go to spam for another, even from the same sender.
Gmail heavily relies on this to determine trust. A poor reputation signals to mailbox providers (MBPs) that your emails might be unwanted, leading to stricter filtering or outright blocking (blocklisting).
Google's sender guidelines explicitly emphasize the importance of these records.
