Why have Mailchimp email open rates dropped and gone to spam in Gmail recently?
Michael Ko
Co-founder & CEO, Suped
Published 5 May 2025
Updated 16 Aug 2025
7 min read
Many email marketers using Mailchimp have recently observed a concerning trend: email open rates plummeting and messages ending up in Gmail spam folders. This isn't an isolated incident, and it points to larger shifts in how inbox providers, particularly Google, are evaluating incoming mail. It is crucial for senders to understand the underlying causes and adapt their strategies.
The challenge of getting emails into the inbox is an ongoing battle, and recent changes by major mailbox providers have made it even more complex. While some issues can be attributed to Mailchimp specifically, many reflect broader industry trends and new filtering mechanisms. Let's delve into why these changes are happening and what you can do to improve your email deliverability.
Recent shifts in Gmail's filtering
I've seen discussions suggesting that Gmail has significantly tightened its filters recently. This isn't necessarily a targeted attack on Mailchimp, but rather a system-wide adjustment that impacts many email senders. The goal is often to reduce unwanted mail for users, but it can unfortunately lead to legitimate emails being caught in the net.
One key factor is how Gmail's algorithms interpret engagement. If your subscribers are not consistently interacting with your emails (e.g., clicking links, replying), even if they open them, Gmail might start routing those messages to the spam folder. This explains scenarios where open rates drop but click-through rates remain stable.
Furthermore, there has been a significant shift in the reliability of open rates. Mailchimp, like many other Email Service Providers (ESPs), relies on a tiny tracking pixel to register an open. Privacy-focused features, particularly Apple Mail Privacy Protection, can artificially inflate reported open rates or prevent them from being accurately tracked. This means a perceived drop in open rates might not always reflect a deliverability issue, but rather changes in how opens are measured. Nevertheless, if emails are going to spam, it's a clear indicator of a deliverability problem. Some argue that this doesn't break open tracking, but it certainly changes how we interpret the data.
Mailchimp's statement on Gmail changes
Mailchimp communicated that a change in Gmail's spam filtering led to an increase in false positives for some users. They confirmed they worked with Google to deploy a fix, which for many, resulted in open rates returning to normal levels. This indicates that some of the recent issues were indeed due to adjustments at Google's end, which Mailchimp was actively addressing. However, ongoing monitoring of your domain reputation through tools like Google Postmaster Tools remains essential.
Authentication and reputation fundamentals
Email authentication is the bedrock of good deliverability. If your emails are not properly authenticated with SPF, DKIM, and DMARC, they are highly likely to land in spam. Mailchimp, like other ESPs, uses its own authentication, but you should also verify your custom domain's records are set up correctly. Some Mailchimp users found they were on legacy authentication settings, which needed updating to align with current best practices.
Even if your Google Postmaster Tools shows a perfect domain reputation, new contacts may still receive your emails in spam. This often happens because there's no prior sending history with that specific recipient. Building a positive sending reputation takes time and consistent good sending practices. Additionally, if you're on a shared IP (which is common with ESPs like Mailchimp), your deliverability can be influenced by the sending habits of other users on that same IP address. This can lead to your emails being caught by IP-related blocklists, even if your practices are sound.
Warm up new IPs: If you're using new dedicated IPs, gradually increase sending volume to build reputation.
Content quality and recipient engagement
The content of your email plays a huge role in deliverability. Spam filters are highly sophisticated and analyze everything from your subject line and body text to links and images. Overuse of promotional language, excessive exclamation marks, or misleading subject lines can trigger these filters, regardless of your sender reputation. Ensure your content is relevant, valuable, and directly addresses the needs of your audience.
Maintaining an engaged list is more crucial than ever. Inbox providers are increasingly prioritizing recipient engagement as a primary signal for inbox placement. If your subscribers aren't consistently opening, clicking, or otherwise interacting with your emails, this can signal to Gmail (and other providers) that your emails are not desired, leading to lower open rates and increased spam placements. Regularly cleaning your email list to remove unengaged or inactive subscribers is a vital practice for maintaining a healthy sender reputation and improving your email deliverability. Google's plans to delete inactive Gmail accounts further highlight the importance of sending to an active audience.
Best practices for content and engagement
Personalize emails: Tailor content to individual recipients to increase relevance and engagement.
Optimize subject lines: Make them clear, concise, and engaging, avoiding spam triggers.
Segment your audience: Send targeted campaigns to different groups based on their interests.
Encourage interaction: Include clear calls to action that prompt clicks or replies.
Mailchimp and broader deliverability trends
While the focus might be on Mailchimp and Gmail, it's important to recognize that deliverability challenges can be widespread. Some users have reported seeing increased issues not only with Gmail, but also with other major providers like Outlook, Office 365, and Yahoo. This suggests a broader tightening of security measures across the email ecosystem, potentially in response to new scam trends. Understanding why your emails fail is essential.
While being listed on an IP-related blacklist (or blocklist) when using a shared IP through an ESP can be pretty standard, it doesn't mean it has no impact. A low-level blacklist listing might not immediately send all your emails to spam, but it contributes to a negative overall sender score, making you more vulnerable to stricter filtering by providers like Gmail when they tighten their systems. Regular blocklist checking is an important part of a proactive deliverability strategy.
Issue
Impact on open rates
Impact on spam placement
Poor Authentication
Lowered
Higher
Low Engagement
Lowered
Higher
Shared IP Blocklists
Varied (can be significant)
Higher
Spammy Content
Lowered
Higher
Views from the trenches
Best practices
Maintain an impeccably clean and engaged email list to enhance sender reputation.
Regularly review and update your email authentication records: SPF, DKIM, and DMARC.
Monitor your domain and IP reputation using tools like Google Postmaster Tools for early warnings.
Segment your audience and personalize content to increase relevance and interaction.
Proactively test your email deliverability across various mailbox providers.
Common pitfalls
Ignoring subtle drops in open rates or increases in spam folder placement.
Relying solely on open rates as a measure of email success due to privacy changes.
Failing to update legacy email authentication settings when using an ESP like Mailchimp.
Not cleaning your list of unengaged or inactive subscribers regularly, leading to bounces.
Assuming deliverability issues are isolated to one provider, when they may be systemic.
Expert tips
Focus on increasing click-through rates (CTR) and other engagement metrics for a more accurate view of campaign performance.
For shared IP issues, analyze your sending patterns and list quality, as your behavior influences the shared pool.
Consider gradually re-engaging or removing inactive subscribers rather than sending to them indefinitely.
Review your email content for common spam triggers and ensure it aligns with recipient expectations.
Remember that continuous monitoring and adaptation are key to navigating evolving email filters.
Expert view
Expert from Email Geeks says that Mailchimp's own testing did not show widespread spam placement issues for all users, indicating that any problems may be specific to certain accounts or sending patterns.
2023-05-31 - Email Geeks
Marketer view
Marketer from Email Geeks says they noticed a drastic drop in open rates for Gmail users, sometimes from 30-40% down to 5-10% around late May, suggesting a significant shift.
2023-05-29 - Email Geeks
Moving forward: Strategies for improvement
The recent drops in Mailchimp email open rates and increased Gmail spam placements are a symptom of an evolving email landscape. It's not always a single, identifiable cause, but rather a combination of factors including tightened Gmail filters, the critical importance of email authentication, and the increasing weight of recipient engagement.
For email marketers, this means shifting focus from merely sending emails to actively cultivating a healthy sender reputation and engaging with a responsive audience. By addressing technical configurations, refining content, and diligently managing your email lists, you can navigate these challenges and ensure your messages consistently reach the inbox, where they can make an impact. This proactive approach will help you maintain strong email deliverability, even as the rules continue to evolve.
Mailchimp have recently observed a concerning trend: email open rates plummeting and messages ending up in 
Gmail spam folders. This isn't an isolated incident, and it points to larger shifts in how inbox providers, particularly Google, are evaluating incoming mail. It is crucial for senders to understand the underlying causes and adapt their strategies.
Outlook, Office 365, and 
Yahoo. This suggests a broader tightening of security measures across the email ecosystem, potentially in response to new scam trends. Understanding why your emails fail is essential.
