How to estimate real open rates with Apple Mail Privacy Protection (MPP) and image caching?
Matthew Whittaker
Co-founder & CTO, Suped
Published 28 May 2025
Updated 18 Aug 2025
8 min read
The landscape of email marketing metrics has changed significantly, particularly with the introduction of Apple Mail Privacy Protection (MPP) in iOS 15. This feature fundamentally altered how email open rates are tracked, primarily due to its image caching and pre-fetching mechanisms. For those of us who rely on accurate engagement data, it's become crucial to understand these changes and adapt our measurement strategies.
Before MPP, an open was typically registered when a tiny, invisible tracking pixel, embedded in the email, was loaded. This pixel would communicate back to the sender's server, signaling that the email had been opened. It was a straightforward, though not always perfect, method for gauging initial recipient interest. However, with Apple's privacy enhancements, this traditional approach now leads to inflated and often misleading open rate figures.
The challenge for email marketers and deliverability specialists is to distinguish between genuine recipient engagement and automated, privacy-driven pixel loads. It's about finding ways to accurately measure email open rates in a post-MPP world. This guide explores how MPP affects open rates and offers practical strategies to estimate actual engagement.
Understanding Apple Mail Privacy Protection (MPP)
Apple Mail Privacy Protection works by pre-loading email content, including tracking pixels, through a proxy server before the user even opens the email. This happens regardless of whether the recipient actually views the message. For senders, this means every email sent to an Apple Mail user (on iOS 15+, iPadOS 15+, and macOS Monterey or newer) appears to be opened, significantly inflating reported open rates. It effectively anonymizes the user's IP address and masks their actual open behavior, making it nearly impossible to determine true engagement based solely on the open pixel.
It's important to note that MPP specifically impacts emails opened within the Apple Mail application, regardless of the email service provider (ESP) or domain. This means someone checking their Gmail on their iPhone's Mail app will trigger an MPP open, whereas someone checking that same Gmail account via the Gmail app or web interface will not. This distinction is vital for understanding the true scope of the impact on your data. Different email service providers handle Apple MPP opens in varied ways, with some offering specific filters or reporting adjustments.
The key takeaway is that an open, post-MPP, no longer reliably indicates active engagement from a user within the Apple Mail ecosystem. It signifies that Apple's proxy server retrieved the email content. This leads to inflated open rates that can reach as high as 70-75% due to false opens, blurring the line between actual interest and automated activity. This also differs from Gmail's image caching, which while affecting tracking, does so differently.
The challenges of traditional open rate metrics
For years, email marketers have relied on open rates as a primary indicator of campaign success and audience engagement. We used them to measure subject line effectiveness, send time optimization, and even inbox placement. However, with MPP, this metric is no longer a standalone indicator of recipient interest for a significant portion of your audience. The inflated numbers can obscure actual performance, making it difficult to assess what truly resonates with your subscribers.
This shift impacts various aspects of email marketing. A/B testing subject lines, which often relies on open rates, becomes less reliable. Segmentation strategies based on open behavior may need re-evaluation. Campaign reporting can show seemingly high open rates, leading to a false sense of security regarding engagement. Understanding how MPP categorizes machine opens is essential for accurate analysis.
The challenge extends beyond just vanity metrics, however. Deliverability itself can be influenced by perceived engagement. While MPP opens might seem to confirm delivery, it's a passive signal. Inbox providers often consider active engagement (like clicks, replies, or adding to contacts) as stronger indicators of sender reputation. Inflated open rates could potentially mask deeper issues with actual recipient engagement and could even affect IP warmup strategy and sender reputation if not properly understood.
Strategies for estimating true engagement
With the limitations of open rates, shifting focus to more reliable engagement metrics is crucial. Click-through rate (CTR) is now arguably the most important metric for assessing campaign effectiveness. Unlike opens, clicks are still directly attributable to user action, as MPP does not interfere with click tracking. This makes CTR a strong indicator of how well your content resonates and drives desired actions. Other metrics like conversions, replies, and even unsubscribes (as a sign of active engagement, albeit negative) become more valuable.
To estimate real open rates, you can segment your audience based on their email client and device usage. While exact figures for Apple Mail users are elusive, analyzing the engagement of non-Apple Mail users can provide a baseline. You can then apply this baseline to your estimated Apple Mail audience to get a more realistic open rate for your entire list. For example, if your non-Apple segment has a 25% open rate, and 40% of your list uses Apple Mail, you could estimate a true open rate closer to that non-Apple figure for the Apple segment.
Furthermore, inferring engagement from other actions like website visits, purchases, or interactions with other marketing channels can provide a holistic view. If a user consistently clicks links in your emails but shows up as an MPP open, it's a strong signal of genuine interest. This approach requires more sophisticated tracking and data integration, but it offers a richer understanding of your audience's behavior. Adjusting your open rate calculations to factor in these nuances is key.
Some email service providers have begun to implement features to help distinguish MPP opens from genuine ones, though the accuracy varies. Utilizing these features, or applying a formula to exclude machine-generated opens, can provide a cleaner dataset for analysis. Always aim for a blend of metrics to get the most comprehensive view of your campaign performance.
Adjusting your email strategy post-MPP
Adapting your email strategy post-MPP means prioritizing engagement beyond the open. This involves crafting compelling content that encourages clicks, rather than just relying on eye-catching subject lines to get the email opened. Focus on clear calls to action, valuable content, and a seamless user experience once they click through.
It's also an opportunity to refine your segmentation and personalization efforts. Instead of segmenting by 'opened vs. not opened', consider segments like 'clicked vs. not clicked', 'purchased vs. not purchased', or 'visited website vs. not visited'. These actions provide more meaningful insights into subscriber intent and allow for more targeted and effective campaigns. You can increase your email click-through rate by focusing on these actionable metrics.
Maintaining a clean and engaged list remains paramount. Regularly pruning inactive subscribers (those who haven't clicked or engaged in other ways over a long period) helps ensure your messages reach genuinely interested recipients, improving overall deliverability and reducing the likelihood of being flagged as spam. This proactive approach helps boost email deliverability rates.
Views from the trenches
Best practices
Focus on alternative metrics like click-through rates and conversions, as they are not impacted by MPP and provide truer engagement insights.
Segment your audience by email client if possible to analyze non-Apple Mail users for a more accurate baseline of open behavior.
Prioritize compelling email content and clear calls to action to drive genuine clicks and deeper engagement.
Regularly clean your email list by removing unengaged subscribers who show no active interaction.
Utilize features within your ESP that attempt to filter or categorize MPP-generated opens for clearer reporting.
Common pitfalls
Relying solely on open rates as a key performance indicator, as they are significantly inflated by Apple Mail Privacy Protection.
Failing to segment your audience and analyze engagement across different email clients, leading to misinterpretations of data.
Not adjusting your A/B testing strategies to account for the unreliability of open rate metrics post-MPP.
Ignoring the impact of MPP on historical data trends, making month-over-month comparisons misleading.
Overlooking other valuable engagement signals such as website visits, replies, or social media interactions from email recipients.
Expert tips
Consider MPP opens as a confirmation of email delivery rather than active engagement, especially for Apple Mail users.
Develop a comprehensive engagement score for each subscriber by combining multiple metrics, including clicks, conversions, and website activity.
Experiment with content formats that inherently require interaction, such as quizzes or interactive elements, to gauge true interest.
Use a multi-channel attribution model to understand how email contributes to overall customer journeys beyond simple opens or clicks.
Regularly review industry benchmarks and reports on MPP's evolving impact to stay informed on the latest data trends.
Expert view
An expert from Email Geeks says that you will not actually achieve 100% open rates, even with Apple Mail Privacy Protection enabled.
2024-09-17 - Email Geeks
Expert view
An expert from Email Geeks says that no one definitively knows the true open rate because open pixel image loads have always been, and will remain, an estimate.
2024-09-17 - Email Geeks
Navigating the future of email metrics
The advent of Apple Mail Privacy Protection (MPP) represents a significant shift in email marketing, signaling a move away from open rates as a primary metric for engagement. While it presents challenges, it also encourages a more sophisticated approach to understanding your audience.
By embracing alternative metrics like click-through rates, conversion rates, and other forms of active engagement, you can gain a more accurate and actionable understanding of your campaign performance. This adaptation not only helps in navigating the complexities of MPP but also leads to more effective and results-driven email marketing strategies in the long run.
Apple Mail user (on iOS 15+, iPadOS 15+, and macOS Monterey or newer) appears to be opened, significantly inflating reported open rates. It effectively anonymizes the user's IP address and masks their actual open behavior, making it nearly impossible to determine true engagement based solely on the open pixel.
Apple Mail application, regardless of the email service provider (ESP) or domain. This means someone checking their Gmail on their iPhone's Mail app will trigger an MPP open, whereas someone checking that same Gmail account via the Gmail app or web interface will not. This distinction is vital for understanding the true scope of the impact on your data. Different email service providers handle Apple MPP opens in varied ways, with some offering specific filters or reporting adjustments.
