How do AI assistants and MPP impact email open rates, and what are better metrics to measure outbound campaign effectiveness?
Matthew Whittaker
Co-founder & CTO, Suped
Published 15 Jun 2025
Updated 18 Aug 2025
7 min read
Email open rates have long been a foundational metric for understanding audience engagement and campaign performance. For years, marketers relied on them to gauge initial interest. However, the landscape of email tracking has undergone significant shifts, primarily due to privacy enhancements like Apple Mail Privacy Protection (MPP) and the increasing sophistication of AI assistants.
These changes have fundamentally altered how open rates are measured, often leading to inflated and misleading figures. My focus today is on understanding how these technologies impact what we see in our analytics and, more importantly, what metrics truly matter for assessing the effectiveness of outbound email campaigns.
It's a common misconception that a high open rate always signifies genuine human engagement. As we delve deeper, it becomes clear why relying solely on this metric can lead to flawed strategies and misinterpretations of campaign success.
The shifting landscape of email open rates
Apple Mail Privacy Protection, introduced with iOS 15, significantly changed how email opens are tracked. Before MPP, an email open was typically registered when the tracking pixel (a tiny, invisible image) embedded in the email was downloaded by the recipient's email client. This usually happened when a user opened the email and images were displayed.
MPP, however, preloads content, including tracking pixels, when an email is delivered to an Apple Mail user's inbox, regardless of whether the user actually opens the email. This means a reported open from an Apple Mail user does not necessarily indicate genuine engagement. This automatic pixel loading is done through a proxy server, anonymizing the user's IP address and location. You can learn more about how MPP affects open and click tracking.
Similarly, AI assistants and advanced email clients often employ similar pre-fetching mechanisms. Tools designed to organize, summarize, or analyze emails may also trigger tracking pixels without human interaction. This can lead to a phenomenon where you see multiple opens for a single email, one from MPP and another from the AI agent, further inflating your perceived open rates.
The impact on open rates
The immediate consequence of MPP and AI assistants is an artificial inflation of email open rates. If your audience includes a significant number of Apple Mail users or those using AI-powered email tools, your open rate metrics will likely show an increase that doesn't reflect actual human engagement. This means that a seemingly high open rate can be deceptive, as it doesn't accurately indicate how many recipients genuinely saw or read your message.
Inflated data: Reported open rates might be higher than actual human engagement.
Misleading performance: Campaigns might appear more successful than they are, leading to misguided optimizations.
Even before MPP and AI assistants, email open rates were never a perfectly accurate indicator of human engagement. Issues like images being blocked by default in some email clients or recipients reading plain-text versions of emails meant that not every genuine open was recorded. Conversely, some opens were triggered by security scans or email preview panes, not by human interaction. This is why some experts have advised against obsessing over open rates for years.
The primary purpose of an email, especially in outbound campaigns, is not merely to be opened, but to elicit a specific action or response. An email that is opened but leads to no further engagement is, in many ways, just as ineffective as one that goes unopened. Therefore, focusing on metrics that reflect deeper engagement and ultimately contribute to your campaign objectives is essential.
For B2B outbound campaigns, where the goal is often lead generation, sales, or building relationships, the traditional open rate has become even less reliable. My advice is to consider it a directional metric at best, and turn your attention to indicators that more directly correlate with your business goals.
Traditional view of open rates
Primary engagement metric: Often considered the first indicator of interest.
Deliverability signal: High opens were thought to correlate with good inbox placement.
Content effectiveness: Used to assess subject line and preheader text performance.
Modern view of open rates
Influenced by proxies: Artificially inflated by MPP and AI assistants.
Limited insight: Does not accurately reflect human engagement or actual readership.
Focus on action: Better to prioritize metrics that show active user interaction.
Better metrics for outbound campaign effectiveness
For outbound campaigns, especially in a B2B context, the goal isn't just to get an email delivered, it's to start a conversation or drive a specific business outcome. Therefore, we need to shift our focus to metrics that truly reflect meaningful interaction. Here are some key metrics I recommend tracking:
Click-through rate (CTR): This is the percentage of recipients who clicked on a link within your email. A click requires a deliberate action by the recipient, making it a much stronger indicator of interest than an open. You can learn how to increase your email click-through rate.
Conversion rate: This measures the percentage of recipients who complete a desired action after clicking, such as filling out a form, making a purchase, or scheduling a demo. This is the ultimate measure of campaign effectiveness for many outbound efforts.
Reply rate: Especially for B2B cold outreach, the reply rate (and specifically, the positive reply rate) is crucial. A reply signifies direct engagement and interest from the recipient. This is where the true value of your outreach is often realized.
Spam complaint rate: While not a direct engagement metric, a low spam complaint rate indicates that your emails are perceived as valuable and relevant, contributing positively to your sender reputation. High complaint rates can lead to your emails being blocklisted or sent to the spam folder.
Unsubscribe rate: A low unsubscribe rate suggests that your content remains relevant to your audience over time. A high rate indicates disengagement or irrelevant content.
These metrics offer a more accurate representation of actual recipient engagement and campaign effectiveness, helping you optimize your strategies for real business impact rather than superficial opens. It's about measuring outcomes, not just initial interactions. For a broader understanding of important metrics, consider exploring KPIs that actually matter.
Metric
Why it matters for outbound campaigns
Impact of AI/MPP
Open rate
Historically, initial interest and deliverability signal.
Significantly inflated, unreliable indicator of human engagement.
Click-through rate (CTR)
Strong indicator of interest in your content/offer.
Less affected, as most clicks require human interaction. Some bot clicks can occur.
Conversion rate
Direct measure of campaign success towards business goals.
Not directly impacted; reflects true recipient action post-click.
Reply rate
Crucial for B2B; signifies direct engagement and potential lead.
Not impacted; a human action.
Adapting your measurement strategy
To accurately measure your outbound campaign effectiveness in this new environment, you need to adapt your strategy. First, accept that open rates, while still present in reports, are no longer the single source of truth for engagement. Instead, treat them as a high-level indicator that your emails are generally landing in the inbox, but not necessarily being read.
Second, shift your reporting dashboards to prioritize CTR, conversion rate, and reply rates. These metrics provide clear, actionable insights into how well your content resonates and drives desired outcomes. For B2B campaigns, a high reply rate signifies direct interest and a potential qualified lead, which is far more valuable than a mere open.
Third, consider deeper analysis for engagement. Some advanced analytics platforms might allow you to differentiate between genuine opens and proxy opens, often by analyzing user-agent strings or other technical data. However, for most marketers, focusing on post-open actions is a more practical approach. It is also important to remember that not every high open rate means high engagement.
The path forward for email marketers
The evolution of email privacy features and the rise of AI assistants mark a pivotal moment for email marketing. While open rates have become increasingly unreliable, this challenge presents an opportunity to focus on more meaningful metrics that truly reflect campaign effectiveness. By prioritizing clicks, conversions, and replies, you can gain a clearer understanding of your audience's true engagement and optimize your outbound efforts for tangible business results. My recommendation is to embrace this shift and leverage these richer insights to build more effective and impactful email strategies.
Views from the trenches
Best practices
Always include a clear call-to-action (CTA) in your emails to make tracking clicks and conversions easier and more accurate.
Segment your audience based on known email clients or devices to analyze the impact of MPP more specifically.
Test different subject lines and preheader texts, but measure their effectiveness through click and reply rates.
Common pitfalls
Over-relying on open rates as the sole measure of email campaign success.
Failing to adapt reporting dashboards to include more relevant engagement metrics.
Misinterpreting high open rates as genuine interest when they are inflated by proxy opens.
Expert tips
Implement robust CRM integration to tie email campaign performance directly to sales outcomes and lead quality.
Consider A/B testing elements beyond the subject line, such as email body content and CTA placement, to optimize for clicks and replies.
Analyze email deliverability beyond open rates by monitoring bounce rates, spam complaint rates, and direct inbox placement tests.
Marketer view
Marketer from Email Geeks says that if you have full event logs, checking the user-agent can help differentiate between genuine and proxy opens.
2024-02-07 - Email Geeks
Expert view
Expert from Email Geeks says that depending on how the AI agent works, you might see two opens per email: one from MPP and one from the AI agent.
