Are prefetch opens and proxy opens the same thing?

While related, they are not precisely the same. Prefetch opens refer to automated image loading by email clients before a user views the email. Proxy opens involve an intermediary server fetching email content to hide user details. Both can contribute to inflated open rates and often occur simultaneously, such as with Apple Mail Privacy Protection.

Which email clients or services use prefetch and proxy opens?

Many email clients, like Gmail with its image proxy , and Apple Mail Privacy Protection (MPP) , use prefetching and proxying. These features are designed to enhance user privacy and improve loading times, but they significantly impact the accuracy of reported open rates by triggering opens without actual human interaction.

What if my open rates decrease, but my click-through rates stay the same?

If your open rates decrease but your click-through rates remain stable, it suggests that the drop in opens is likely due to a reduction in automated prefetch or proxy activity, rather than a decline in actual human engagement. This scenario means your emails are still reaching and engaging recipients, but the way opens are being reported has changed, making them more accurate. It's not necessarily a negative sign, but a reflection of evolving privacy measures.

Do proxy opens confirm email inbox delivery or influence ISP perception?

No, proxy opens do not necessarily confirm inbox delivery or influence ISP perception in the same way human opens do. While a proxy open might indicate the email passed initial filters, it doesn't confirm it landed in the primary inbox or was seen by the recipient. ISPs typically rely on a broader range of signals, including sender reputation, spam complaints, and genuine engagement, to determine inbox placement. Relying on proxy opens for deliverability insights can be misleading.

What metrics should I focus on instead of open rates?

Focus on metrics beyond opens that indicate true engagement, such as click-through rates, conversion rates, and replies. Regularly clean your email list to maintain hygiene and improve deliverability. Ensure your email authentication (SPF, DKIM, DMARC) is properly configured. Segment your audience and tailor content to increase relevance, leading to more meaningful interactions. These practices will provide a more accurate picture of your email campaign performance.

What are prefetch and proxy opens and what causes a decrease in email open rates? - Technical - Email deliverability - Knowledge base

Email open rates have long been a cornerstone metric for marketers, indicating how many recipients engaged with their messages. However, in recent years, their reliability has become increasingly questionable. This shift is largely due to the rise of advanced privacy features and technical changes in how email clients handle messages, introducing concepts like prefetch and proxy opens. Understanding these mechanisms is crucial for accurately interpreting your email performance and adjusting your strategies accordingly.

The traditional tracking pixel, a tiny 1x1 image embedded in emails, has been the primary method for recording an open. When the email client loads this image, it registers as an open. But what happens when that image is loaded without direct human interaction or through an intermediary?

What are prefetch opens?

Prefetch opens, often referred to as non-human interaction (NHI) opens, occur when an email client automatically retrieves images within an email before a user consciously opens or views the message. This automated fetching is designed to improve user experience, making emails load faster when a user eventually clicks on them. It can also serve purposes like content filtering and spam detection by allowing the email service provider (ESP) to scan image content proactively.

For instance, an email client might prefetch images for all emails in a user's inbox, even those in a promotional tab, without the user ever scrolling to or clicking on them. This activity registers as an open, inflating the open rate reported by email service providers. The challenge is that these opens do not necessarily reflect actual human engagement, leading to a skewed perception of campaign performance.

This prefetching can happen multiple times, especially if a user accesses their email across various devices or clients. Each time a client prefetches the images, it could be counted as another open, further contributing to inflated metrics that don't correspond to a human viewing the email.

What are proxy opens?

Proxy opens, on the other hand, refer to instances where an email client fetches email images through an intermediary server, or a proxy, rather than directly from the sender's server. The primary motivation behind proxying is to enhance user privacy by masking the recipient's IP address, device details, and geographic location. This prevents senders from gathering granular data about the recipient's interaction with the email.

The most prominent example of this is Apple Mail Privacy Protection (MPP), which routes all email image loads through a proxy server for users who enable the feature. This means that instead of seeing the user's actual IP address, email marketers only see the IP address of Apple's proxy server. This obscures valuable insights into the recipient's location or the device they used to open the email, impacting data-driven decisions.

It is important to note that prefetch and proxy opens are not mutually exclusive. In fact, they often occur in tandem. For example, Apple's MPP both prefetches images and proxies the requests, leading to a complex scenario for email marketers. This dual mechanism creates significant uncertainty about whether an email was truly opened by a human, when it was opened, and from where.

A good resource to understand prefetching and proxies is Word to the Wise, which provides a detailed breakdown of how these technologies work. They explain that a pre-fetched open is a NHI (non-human interaction) open where automation retrieves the image before the user sees it, while a proxied open involves an intermediary system fetching the image on behalf of the user.

How do these impact open rates?

The most significant impact of prefetch and proxy opens is the artificial inflation of open rates. What might appear as a surge in engagement could, in reality, be automated fetches. This makes it challenging to gauge the true effectiveness of email campaigns and to segment audiences based on genuine open behavior.

When your reporting shows a high open rate, it no longer definitively means that a human eye has seen your email. This uncertainty necessitates a shift in how email marketers evaluate their performance. Relying solely on open rates can lead to misguided conclusions about subscriber engagement and the overall health of your email program.

This leads to a paradox: while open rates might seem high due to automated fetches, the actual, human-driven engagement might be stagnant or even decreasing. It's crucial to understand the nuances of these technical changes to avoid misinterpreting your data.

Traditional open rate

Historically, a high open rate implied that recipients were actively viewing your emails. It was a direct measure of initial engagement.

Clear engagement: Directly correlated with human interaction.
Location data: IP addresses provided insights into recipient geography.

Open rates today

Now, open rates can be inflated by automated prefetching and proxy services, making them a less reliable indicator of true engagement.

Inflated metrics: Does not always mean human interaction.
Obscured data: Location and device information are often masked by proxies.

Marketing.org.nz provides insights into how Mail Privacy Protection (MPP) can cause emails to appear immediately opened, over-inflating rates and triggering further automated actions. This highlights the need to re-evaluate how we measure email performance.

Factors causing a decrease in actual email open rates

Beyond the technical inflation caused by prefetch and proxy opens, several factors can lead to a genuine decrease in your email open rates. These are often related to your sender reputation, list quality, and content strategy.

Sender reputation: A decline in your sender reputation can cause internet service providers (ISPs) to filter your emails into spam folders or block them outright. Factors like high bounce rates, spam complaints, and sending to inactive addresses contribute to a poor reputation.
List hygiene: Sending to an outdated or unengaged list means fewer real people are opening your emails. Regular list cleaning is essential to remove invalid or inactive subscribers. Poor list hygiene can lead to hitting spam traps, which can severely damage your deliverability and lead to being blocklisted (or blacklisted).
Content relevance: If your email content, subject lines, or send frequency don't align with subscriber expectations, they are less likely to open your emails over time. A decline in engagement often precedes a drop in opens.
Spam filter changes: ISPs constantly update their spam filtering algorithms. A sudden change in your open rates could indicate that your emails are now being routed to the spam or promotions folder more frequently. This is particularly relevant for Gmail open rates due to its sophisticated filtering.

When facing a drop in open rates, it's vital to investigate beyond the raw numbers. Consider a holistic view of your email program, from authentication to content, to identify the root cause. This includes checking your DMARC, SPF, and DKIM records for proper configuration, as authentication failures can also impact inbox placement and, consequently, real opens.

Views from the trenches

Best practices

Monitor click-through rates (CTR) and conversions as primary engagement metrics, rather than relying solely on open rates.

Segment your audience based on genuine engagement, not just reported opens, to target active subscribers.

Regularly clean your email list to remove unengaged subscribers and invalid addresses, which improves deliverability.

Implement strong email authentication (DMARC, SPF, DKIM) to build and maintain a positive sender reputation.

Test different subject lines and content to improve actual human engagement, not just automated opens.

Common pitfalls

Over-reliance on open rates as the sole measure of email campaign success leads to misleading performance evaluations.

Ignoring list hygiene practices, which results in higher bounce rates, spam complaints, and lower actual engagement.

Failing to adapt to privacy changes like Apple MPP, leading to a misunderstanding of email performance data.

Not segmenting email lists by recipient engagement, resulting in sending to inactive users and hurting sender reputation.

Misinterpreting a drop in reported open rates as a deliverability issue, when it might be a shift in automated prefetching.

Expert tips

When analyzing open rate fluctuations, always cross-reference with your click-through rates. If clicks are stable despite open rate changes, it's likely a reporting anomaly due to prefetch/proxy activity.

Break down your open data by mailbox provider. This can help identify if a drop is specific to a certain provider (e.g., Google or Apple) which might indicate changes in their prefetching or proxy behavior.

Focus on active engagement metrics like clicks, conversions, and replies. These metrics are harder to inflate and provide a clearer picture of subscriber interest.

Educate your team about the limitations of open rates in the current email landscape. Shift the conversation towards more meaningful engagement indicators.

Consider a shift towards a more holistic deliverability strategy that emphasizes inbox placement and subscriber engagement, rather than just raw open numbers.

Marketer view

Marketer from Email Geeks says prefetch opens happen as the email is being delivered, not necessarily when the end user opens it. Proxy opens, meanwhile, mask the details of the user's device and location, and usually both types of opens are proxied.

2024-08-04 - Email Geeks

Expert view

Expert from Email Geeks says pre-fetching occurs when the email client prepares the message for display, sometimes before the user views it. This process can happen multiple times for users with several devices. Proxies conceal a user's individual location and possibly device specifics, as seen with Apple's image loads being routed through their proxy network.

2024-08-04 - Email Geeks

Moving beyond open rates

Given the growing prevalence of prefetch and proxy opens, it's time to adjust our perspective on email success. While open rates will likely remain a visible metric, they should no longer be the sole indicator of engagement or deliverability.

Instead, prioritize metrics that reflect deeper engagement, such as click-through rates (CTR), conversion rates, and replies. These actions require direct human interaction and are less susceptible to inflation from automated processes. By focusing on these indicators, you gain a more accurate understanding of how your audience truly interacts with your email campaigns.

Ultimately, the goal is to drive meaningful interactions and build lasting relationships with your subscribers. Adapting your measurement strategy to account for modern email client behaviors will help you make more informed decisions and achieve better results.