Why are Hotmail open rates declining and what is the solution?
Michael Ko
Co-founder & CEO, Suped
Published 6 Jun 2025
Updated 19 Aug 2025
6 min read
Many email marketers have recently seen a notable drop in open rates, particularly for recipients using Hotmail, Outlook, and other Microsoft-affiliated domains. This decline can be frustrating, especially when your email campaigns previously performed well. It's a common issue, and understanding the underlying causes is the first step toward finding effective solutions.
The landscape of email deliverability is constantly evolving, with mailbox providers like Microsoft continually refining their spam filters and inbox placement algorithms. What worked last year, or even last month, might not be as effective today. If you've observed a sudden decrease in how many people open your emails, especially with Hotmail accounts, you're not alone. Let's delve into why this is happening and what strategies you can employ to reverse the trend.
Understanding the challenge with Hotmail
One of the primary reasons for declining open rates, particularly with Microsoft domains like Hotmail and Outlook, stems from increasingly stringent spam filtering and reputation requirements. Mailbox providers prioritize protecting their users from unwanted emails, leading to more aggressive filtering. This means legitimate emails can inadvertently land in the spam folder or not be delivered at all if they don't meet specific criteria. For more insights into these issues, you might find our article on low deliverability and open rates with Hotmail helpful.
Beyond general filtering, privacy changes, such as Apple's Mail Privacy Protection, have significantly impacted how open rates are tracked. These features automatically load images in emails, making it appear as though an email has been opened even if the recipient hasn't seen it. While this doesn't directly cause a decline in actual opens, it can skew your metrics, making it harder to distinguish true engagement. Therefore, while your reported open rates might seem lower, the actual engagement could be higher than what the numbers suggest, or conversely, a true drop could be masked by artificial opens.
Understanding the metrics
The perceived decline in open rates might not always mean fewer people are interacting with your emails. Privacy features can inflate or distort open rate data. Focus on other metrics to gauge true engagement.
Focus on clicks: Monitor click-through rates as a more reliable indicator of active subscriber interest.
Conversions: Track direct actions taken after email interaction, such as purchases or sign-ups.
List growth: Healthy list growth indicates continued interest in your content.
Foundational solutions: authentication and reputation
The cornerstone of strong email deliverability, especially to Microsoft's sensitive mailboxes, lies in proper email authentication. Technologies like Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting & Conformance (DMARC) are crucial. These records prove that you are an authorized sender and help prevent spoofing and phishing, which in turn builds your sender reputation. If you're seeing your email open rate drop suddenly, improper authentication is a common culprit.
Your sender reputation, tied to your IP address and sending domain, directly influences whether your emails reach the inbox or the junk folder. Factors such as spam complaints, bounce rates, and engagement levels all contribute to this reputation. A poor reputation can lead to being listed on a blocklist (or blacklist), which will severely hinder your email deliverability to Hotmail and other providers. Regularly checking your sender reputation and blocklist status is vital.
Implementing a DMARC policy is highly recommended. It provides instructions to receiving mail servers (like Hotmail's) on how to handle emails that fail SPF or DKIM authentication, and it also sends you reports on email authentication failures. This visibility is invaluable for identifying and resolving issues that affect your deliverability. For a simpler explanation, see our guide on DMARC, SPF, and DKIM.
Example DMARC record for monitoring and quarantineTXT
Even with perfect authentication, low engagement from your subscribers, particularly those on Hotmail accounts, can signal to mailbox providers that your content isn't desired. This can lead to your emails being placed in the junk folder, bypassing the inbox entirely. Regularly cleaning your email list to remove inactive subscribers and focusing on sending to an engaged audience is crucial. This practice is often referred to as list hygiene and is a critical factor in deliverability. Our article on declining open rates for Hotmail and Live accounts elaborates on this point.
Mailbox providers, including Microsoft, pay close attention to user engagement signals. If subscribers rarely open or click your emails, or worse, mark them as spam, it negatively impacts your sender reputation. Conversely, positive engagement signals, like opens, clicks, and replies, tell providers that your emails are valuable to recipients. This is why it’s so important to send relevant content.
Spam traps are email addresses specifically designed to catch senders who use poor list management practices. Hitting a spam trap can severely damage your sender reputation and lead to your IP or domain being put on a blacklist (or blocklist). Regularly removing unengaged subscribers and maintaining a double opt-in process for new sign-ups are effective ways to avoid spam traps.
Old list hygiene (less effective)
Infrequent cleaning: Removing inactive subscribers only once or twice a year.
Engagement definition: Considering anyone who opened an email in the past 90 days as engaged.
Ignoring bounces: Not promptly removing hard bounces from the list.
Single opt-in: Allowing subscribers without confirmation, risking spam trap inclusions.
New list hygiene (more effective)
Frequent monitoring: Regularly segmenting and pruning unengaged contacts, possibly every 30 days.
Strict engagement: Defining engagement as clicks or active opens within 15-30 days, especially for Outlook/Hotmail deliverability.
Automated bounce handling: Immediate removal of invalid or non-existent email addresses.
Double opt-in: Requiring email confirmation to ensure valid and interested subscribers.
Sustaining deliverability to Microsoft accounts
Mailbox providers continuously monitor sender behavior. Maintaining consistent sending volumes and frequencies helps build a predictable and positive sending pattern. Sudden spikes in volume or erratic sending schedules can raise red flags and trigger spam filters. This consistency helps establish trust with Hotmail's algorithms and contributes to better inbox placement.
Proactive monitoring of your email performance and deliverability is paramount. Utilize tools that provide insights into your sending reputation, blacklist status, and DMARC reports. This allows you to identify issues early and take corrective action before they severely impact your open rates. Regular checks can help you understand why Hotmail deliverability suddenly dropped for your specific campaigns.
Microsoft's guidelines for senders are also continually updated. Staying informed about changes to their policies and best practices is essential for long-term deliverability. Adhering to these guidelines, which often emphasize good sender reputation and positive user engagement, will help ensure your emails reach the inbox rather than the spam folder.
Views from the trenches
Best practices
Maintain a rigorous email list hygiene schedule by regularly removing inactive subscribers to improve sender reputation and avoid spam traps.
Implement and monitor DMARC, DKIM, and SPF records to ensure proper email authentication and build trust with Hotmail's filters.
Segment your audience based on engagement, sending more frequently to highly engaged users and less often to those who rarely open emails.
Focus on creating highly relevant and personalized content to encourage positive engagement signals like opens and clicks.
Common pitfalls
Failing to implement proper email authentication, leading to emails being marked as spam or rejected by Microsoft servers.
Continuing to send emails to unengaged subscribers, which negatively impacts sender reputation and lowers overall open rates.
Ignoring spam complaints and bounce rates, which are critical indicators of poor list quality or content issues.
Not monitoring deliverability metrics beyond open rates, missing crucial insights into inbox placement and user engagement.
Expert tips
Adjust your definition of 'active' for Microsoft recipients, perhaps reducing the engagement window to 15-30 days to mitigate stricter filtering.
Leverage DMARC reports to identify authentication issues quickly and understand how Microsoft is handling your email traffic.
Conduct A/B tests on subject lines and email content to discover what resonates best with your Hotmail audience and drives higher engagement.
Engage in re-engagement campaigns for inactive subscribers before removing them, providing a chance to re-affirm their interest.
Marketer view
Marketer from Email Geeks says they have been experiencing more issues with Hotmail than usual recently, despite only sending to their best consumers.
August 20, 2020 - Email Geeks
Marketer view
Marketer from Email Geeks says that Microsoft, including Hotmail, is becoming increasingly difficult and stricter with email deliverability, suggesting clients stick to 15-day active engagement criteria.
August 20, 2020 - Email Geeks
Key takeaways for improving open rates
While declining Hotmail open rates can be disheartening, they often signal a need to adapt your email strategy to current deliverability standards. By strengthening your email authentication, maintaining a clean and engaged subscriber list, and consistently monitoring your sender reputation, you can significantly improve your inbox placement and boost your true open rates.
Microsoft continually refining their spam filters and inbox placement algorithms. What worked last year, or even last month, might not be as effective today. If you've observed a sudden decrease in how many people open your emails, especially with Hotmail accounts, you're not alone. Let's delve into why this is happening and what strategies you can employ to reverse the trend.
