iOS 15 and its feature, Mail Privacy Protection, are expected to have quite a large impact on email open rate reporting. 

The intent of this article is to explain the expected impact of the Apple iOS15 release as well as possible remedies.

The iOS 15 version is expected to be released in the fall of 2021 in the window from mid-September to November (September 20th is rumored to be the official release date).

This version of iOS will allow users to “Protect Mail Activity” which will cause open email data reporting to be inaccurate (and inflated) for emails processed through an Apple Mail App regardless of the email service or device used. The adoption is expected to reach 95% or higher (we feel adoption will start at around 80% and scale up over the next few months) because of the way that Apple’s presenting this option to its users.

Here’s how the opt-in screen looks:

This change will only apply to recipients:

  • Using the native Apple iOS Mail App.
  • And only to those who upgraded to iOS 15.
  • And only to those that chose the default Mail Privacy Protection in iOS 15.

Email Funnel

From start to finish, the entire email marketing funnel looks like this:

Next, we’ll discuss which parts of that email funnel Mail Privacy Protection will impact the most and which parts will remain intact. 


This section lists the impact on reporting at each stage of the email funnel. 

1. Email Delivered

Impact: None

Current reporting:

  • Delivery Rate
  • Bounce / Block Rate and Reason

Recommendations: Although No Options are required for current Delivery Reporting, it could be enhanced to offset the iOS15 effect on other areas.

Focus on Delivery rates:

  • Strict bounce logic to deal with soft bounces (and recurring failures)
  • Delivery rate (or Performance) by domain/ISP 
  • Focus on send distribution by domain/ISP
  • Highlight aggressive targeting at a domain/ISP
    • i.e. has 15 recipients targeted in a campaign. Break down the sends.

2. Email Opened

Impact: The release is expected to have a significant impact on the accuracy of all open reporting and open rates may be inflated (inaccurately lifted).

Current reporting:


  • Switch performance reporting to focus on click metrics.
    • Click Reach Rate (30, 90, 180 and 365 days) — percent of subscribers (not percent of clicks) driving clicks per predetermined period.
    • Highlight bot clicks and remove from data — if click is happening immediately after email is received for a subscriber profile, it’s likely a bot. 
  • Use External (non-email) Data — website (or offline) activity attributed back to subscribers. Percent of subscribers engaging with your brand as a whole (not just email).
  • Switch performance reporting to focus on conversion metrics (i.e. revenue, signup, click).
  • Determine your email list correlation between click-through rate and open rate. Use that to estimate future open rates (see calculators below).
  • Track revenue per subscriber as a metric. Also the percentage of subscribers driving revenue.
  • Isolate Apple Mail App users to monitor open rates more accurately. And keep past open rates data as historical baselines.
    • Determine email client breakdown (specifically the percentage of users using Apple Mail Apps).
    • Determine percentage of email on older iOS (not 15) if possible.
    • Isolate all non-Apple Mail users (as a reliable ongoing open rate).
  • Track negative engagement:
    • unsubscribe and unsubscribe to open rates
    • spam complaints (break it down by ISP and ignore Google and any other ISPs that do not have feedback loops)
    • why are people unsubscribing? (feedback after a person unsubscribes)
      • Review these responses regularly to improve future email strategy and experiences for subscribers

Caveats for tracking clicks:

The problem with the heavy “click rate” focus is the user experience.

Emails that use clicks as their primary success metric are, by design, set up to compel a reader to “click-through” and “read more”.

This leads to an email that is less useful to the reader as a stand-alone piece and is (essentially by definition) click-bait. 

For emails that provide real value and content in the inside of their emails (where the email is the actual product), we suggest normalizing “replies” as a part of the email and encouraging easy one-click email feedback (you can still track clicks). 

3. Email Clicked

Impact: None

Current Reporting: 

  • Click rate
  • Click-to-open rate
  • Click reach rate

Recommendations: None required

4. Email Conversion

Impact: Yes. With inflated open rates, this can lead to misleading attributions. The way around this would be to possibly change to a click-only email attribution model

Current Reporting:

  • Signup, purchase or any other defined goal
  • Revenue per email

Recommendations: – None required


We’ve created a few calculators to help you determine how much you should expect your open rate to artificially lift after the launch of iOS 15 and to determine how strong your email list’s correlation is between click-through rate and open rate.

Going forward, you can use this data to estimate a campaign’s open rate based on click-through rate as well as understand more specifically the impact that Mail Privacy Protection will have on your open metrics. 

Click below to access the calculators (and make a copy for yourself). 

To-Do Checklist

  1. How can you identify Apple Client Openers (users who are using the Apple Mail App)?
    • Each ESP will be different.
    • Can you get additional export parameters from your ESP to include email client breakdown (overall/favorite and by email campaign). 
  2. Determine email client breakdown of your list (specifically percentage of users using Apple Mail for email).
    • Isolate all non-Apple mail users (as a reliable open rate).
    • If possible, determine which users are on past versions of iOS.
  3. Define (and implement) other metrics that will be used to measure success. For example, click reach, CTR baselines, revenue tracking, and so on.
  4. Create exclusions or segments based on clicks (as your engagement metric)
  5. Define email types within your marketing channel (and tagging capabilities)
    • Use this for segmentation or exclusions on TAG level
  6. Attribution:
    • If Apple Mail accounts for the minority of total email opens, you may continue monitoring open rates for a few months and no change may be necessary.
    • However, If Apple Mail accounts for the majority of the total email opens, you may explore sending to your Apple Mail segment separately. Based on that segment’s open rates (and performance), you can then decide to switch to click-based attribution (if we’re seeing inflated numbers).
  7. Establish trends between new reporting methods and existing open reporting.
  8. Identify and modify current actions/journeys dependent on open rate:
    • Do you re-send to non-openers? 
    • Do you send Re-engagement campaigns based on an open?
    • Do you have engagement segments/buckets based on opens?
      • Try expanding the criteria to capture engagement and include clicks, website visits, purchases, cart or browse abandonment, etc.
    • Do you have any journeys and/or triggered emails based on an open?
      • Try changing the triggers to clicks or other engagement data or behaviors.
    • Do you run A/B test (winners based on opens)?
      • Try changing to a winner determined by clicks.
      • Note: You can keep opens as the winning criteria if your percentage of Apple Mail users is less than 40% .
    • Do you use send time optimization logic (based on opens)?
      • The impact of this depends on your ESP logic. i.e. Klaviyo: ​​For Smart Send Time, the algorithm doesn’t look at open data on the individual level, so the optimal send time results should remain accurate, but it may take longer to calculate. 
    • Do you purge (or target) dormant subscribers based on open data?

Other Metrics

Now we’ll take a more detailed look at two valuable metrics that you might start using more commonly in place of open rate (or to estimate your open rate via correlation).

Click-Reach Report

Click Reach is the percentage of unique subscribers that click an email over a given period of time (30, 60, 90, or 180 days). This is a good way to get a general idea of what percentage of your subscribers are generally engaged with your emails. 

Click Reach = Unique Clicks Over a Given Period / Unique Sent Over a Given Period

You can also calculate past click reach and compare it to past open reach to determine the level of correlation. 

Our research has indicated a strong correlation (.90 to .95) between click reach and open reach. But this varies based on the brand so we highly recommend crunching your own numbers.

Here’s an example:

Click-Through Rate

The Click-through rate is the percentage of unique subscribers that click on a given email. 

Our research indicates a strong correlation between open rate and click-through rate. The Click-through rate is lower and therefore changes occur in smaller increments.

Final Thoughts: Focus on Outcome-Based Email Marketing

There’s a temptation for email marketers to focus on metrics that aren’t directly related to business outcomes. And so open rate has often been thought of as a vanity metric. 

If you are a marketer for an eCommerce business, for instance, the open rate is only meaningful so far as it impacts the number of people who click and ultimately, the number of people who buy. Opens in and of themselves are not tied to outcomes for eCommerce brands and so perhaps that’s not where we should be focussed anyway. 

Instead, this is a good opportunity for email marketers to put more focus on clicks, sign-ups, revenue, and other result-driving metrics — also keep a close eye on your email deliverability. 

One exception, however, is the email newsletter business model that sells sponsorships in order to make money — those companies have often been required to show high open rate metrics in order to sell sponsorships. In this case, we recommend isolating Apple Mail users to continue tracking open rates reliably and also finding ways to normalize other types of engagement in your emails — whether that’s through one-click email feedback or encouraging subscribers to “reply”.