Why did my email open rates drop significantly in the US segment this Tuesday?
Michael Ko
Co-founder & CEO, Suped
Published 9 Aug 2025
Updated 15 Aug 2025
7 min read
I recently faced a perplexing situation where my email open rates for our US segment plummeted by 40% on a Tuesday, while other segments globally maintained their usual performance. This wasn't the first time I'd seen a localized dip, having experienced a 50% decrease in the US segment previously due to a hurricane and subsequent East Coast outage.
The consistency of opens in Europe and Asia, however, strongly suggested that the issue was specific to the United States. It's common for email marketers to see fluctuations, but such a significant and localized drop demands a closer look. My US audience, consisting of small business owners, SEO experts, and freelancers, typically responds consistently. This specific Tuesday, a newsletter about "Google Entities vs. Keywords" saw its opens halved, raising questions about what unique circumstances in the US could have caused this.
Investigating local factors and audience behavior
When a drop in open rates is isolated to a specific geographic region like the US, my initial thought is always to consider localized events. While it might seem odd for a Tuesday to be affected by an upcoming long weekend, it's a possibility. The US was approaching Labor Day, and even days before a major holiday, people's routines and engagement patterns can shift.
They might be traveling, preparing for time off, or simply less focused on their inboxes. I've seen how holidays can disrupt typical email behavior, leading to lower engagement, even for relevant content.
Another critical consideration is socio-political events or major news. Sometimes, external circumstances can significantly impact how receptive an audience is to marketing emails, even if the content isn't "heavy." For example, if there are major national events or widespread social unrest, people's attention might be diverted away from their inboxes, regardless of the email's topic.
It's also worth noting that the first day of a new month, or the return to school for many children, can create a surge in other types of email traffic and changes in daily routines, leading to more competition in the inbox or simply less time for recipients to engage with non-essential emails. A study by Symanto points out that open rates often peak midweek, suggesting Tuesday's dip was an anomaly against typical patterns.
Mailbox provider insights and deliverability health
A crucial piece of data I noticed was a significant shift in Gmail distribution for the US segment. Typically, Gmail accounts for 62% of our US opens, but on that particular Tuesday, it dropped to 47%. This is a strong indicator that Gmail, specifically for US recipients, might have been treating our emails differently. This could mean they were landing in spam folders or being throttled, even if overall deliverability rates appeared fine elsewhere. You can use tools like Google Postmaster Tools to track issues. Getting familiar with the Spam Rate Dashboard can provide valuable insights.
This brings up the question of blocklists (or blacklists). I heard rumors about issues with Spamhaus that Monday and Tuesday. While Spamhaus did briefly publish some false positives on one of their lists, it was quickly rectified within a few hours. Major mailbox providers like Gmail often use multiple data points, not just one blocklist, for their filtering decisions. So, while a blocklist (or blacklist) issue could contribute, it's less likely to be the sole cause of such a targeted and persistent drop unless the issue was prolonged or severely impacted many IPs used by your ESPs.
For more information on how these lists work, you can refer to a guide on how email blacklists actually work. It's vital to regularly monitor your domain and IP reputation using a blocklist checker to catch these issues early. A sudden drop in opens, especially if coupled with a drop in click-through rates, can signal a deliverability problem. Consistent blocklist monitoring can provide peace of mind and early warnings.
Understanding blocklist impact
Even a brief issue on a major blocklist (or blacklist) like Spamhaus can have ripple effects, especially if your sending IPs or domains were temporarily listed. While Gmail might not directly block based on a single list, other mailboxes or corporate filters might, leading to localized delivery failures. Regular blocklist monitoring is a proactive step to prevent such surprises.
Primary: These lists, like Spamhaus, directly influence filtering decisions for many mailbox providers.
Secondary: Other blacklists are often used by smaller ISPs and corporate networks.
De-listing: If you find your IP or domain on a blocklist (or blacklist), immediate action is required for delisting.
Understanding ESPs and shared infrastructure
The fact that the open rate drop was observed across both GetResponse and Mailchimp for the same US segment is intriguing. While it might seem unlikely for two different email service providers (ESPs) to have simultaneous issues, it's not impossible if they share common infrastructure or routing pathways that are susceptible to regional issues. For instance, if both ESPs utilize data centers in a geographically affected area, or rely on the same upstream internet service providers, a localized network outage or environmental issue could impact both.
Common external factors
Holidays: Long weekends and public holidays, like Labor Day, can shift audience behavior and email engagement patterns.
Socio-political events: Major news or widespread social unrest can divert attention from inboxes, reducing opens, even for unrelated content.
Connectivity: Regional power outages, internet service disruptions, or severe weather can directly prevent recipients from accessing emails.
Internal troubleshooting steps
Audience segmentation: Review the geographic distribution of your US segment to identify if specific states or regions were more affected.
Mailbox provider breakdown: Analyze open rate by domain (e.g., Google.com, Yahoo.com) to pinpoint where the drop occurred most acutely.
ESP communication: Contact GetResponse and Mailchimp support to check for any reported platform-wide issues or regional anomalies.
This unexpected drop, particularly with the Gmail distribution shift, underscores the importance of a comprehensive approach to email deliverability. It's rarely one single factor but rather a combination of elements. Understanding how to troubleshoot sudden drops in email open rates for a large newsletter involves looking at your sender reputation, email content, audience engagement, and external environmental factors.
The multifaceted nature of open rate drops
While a holiday weekend or socio-political events can influence engagement, a 40% drop for a non-sensitive topic like SEO guides is quite steep. It forces us to consider a range of potential causes beyond just current events. Issues such as changes in how recipients interact with your emails, or even privacy changes affecting open rate tracking, could be at play.
Some providers are increasingly using proxy opens, which can skew reported rates. This trend suggests that while open rates remain a key metric, focusing solely on them might not paint the full picture of your email campaign's effectiveness. You should also look at your click-through rates. If click-throughs were also impacted, it further indicates a deliverability or engagement issue. A recent report on email marketing benchmarks shows how open rates have become unreliable due to privacy changes.
Holistic troubleshooting for localized drops
A localized and sudden drop in email open rates, like the one I observed in the US segment on Tuesday, is a complex issue that rarely has a single root cause. It requires looking beyond surface-level metrics and delving into regional factors, mailbox provider behavior, and even the underlying infrastructure of your email service providers. Remember, average email open rates can vary, but a drastic and sudden change demands attention.
To effectively diagnose and remedy such situations, it's essential to combine your internal analytics with external insights. Don't dismiss factors like holidays or current events, but also thoroughly investigate technical aspects like mailbox provider engagement and potential blocklist impacts. A proactive approach to email deliverability, including consistent monitoring and a willingness to adapt your sending strategy, is key to maintaining healthy open rates across all your segments.
Views from the trenches
Best practices
Always segment your audience by geography and monitor performance at that granular level.
Regularly check for any major regional events, holidays, or socio-political situations that might impact recipient behavior.
Communicate with your Email Service Providers (ESPs) to inquire about any localized issues or infrastructure concerns they might be experiencing.
Common pitfalls
Assuming a sudden drop is solely due to content or subject line when other segments perform normally.
Overlooking the impact of external, non-email related events on recipient engagement.
Failing to check for regional blocklist (or blacklist) issues or ISP-specific throttling.
Expert tips
Analyze historical data for the affected segment to identify recurring patterns on specific days or times.
Run small A/B tests on subject lines and send times for the affected segment to see if any changes improve engagement.
Ensure your DMARC, SPF, and DKIM records are correctly configured and aligned to maintain sender reputation.
Expert view
Expert from Email Geeks says that the US was approaching Labor Day, which is a long weekend, and this could affect email engagement patterns leading up to it.
2020-09-04 - Email Geeks
Expert view
Expert from Email Geeks says to investigate mailbox provider distribution, the ESP used, and the frequency and message being sent when encountering localized open rate drops.
Gmail distribution for the US segment. Typically, 
Gmail accounts for 62% of our US opens, but on that particular Tuesday, it dropped to 47%. This is a strong indicator that 
Spamhaus that Monday and Tuesday. While 
GetResponse and 
Mailchimp for the same US segment is intriguing. While it might seem unlikely for two different email service providers (ESPs) to have simultaneous issues, it's not impossible if they share common infrastructure or routing pathways that are susceptible to regional issues. For instance, if both ESPs utilize data centers in a geographically affected area, or rely on the same upstream internet service providers, a localized network outage or environmental issue could impact both.
Yahoo.com) to pinpoint where the drop occurred most acutely.
