Data Privacy & Regulations

Deliverability and engagement: the metrics you need in the wake of iOS 15

Apple’s Mail Privacy Protection—a part of the most recent iOS 15 update—went live on Sept. 20, and already email marketers are noticing the impact on previously relied upon email metrics like open rates. While it will take some time for the full impact of Mail Privacy Protection to be understood, one thing is already certain: This is a gamechanger for email marketers.

What Should I be Measuring with the iOS 15 Change?

Two main metrics should now be measured for every campaign – Deliverability and Engagement.

As open rates become increasingly unreliable measures of campaign impact, it’s absolutely vital that marketers begin to measure email deliverability as a key metric. Before this change was enacted, Open Rates told the story of the middle part of the email journey – Delivered, Opened, Clicked. Without that middle metric, the first step and the final step of the journey are that much more important.

Now, after every campaign, we recommend measuring the deliverability rate of the campaign and then looking at the engagement – the clicks and conversions. As not everyone opens emails, ensuring the email is hitting the inbox is still valuable to get brand awareness and hopefully helping to drive engagement.

Looking Beyond Open Rates

Back in June, when Mail Privacy Protection was initially announced, Data Axle provided background and guidance as to what email marketers could expect at a high level. (See our original post here.) Now that the update is upon us, let’s dig deeper into the tactical implications.

At a high level, Mail Privacy Protection allows Apple Mail users to opt in and choose not to share information about their behaviors that are typically gathered through email pixels. This is a big deal, given that Apple Mail makes up close to 60 percent of all desktop email opens and the iPhone is the leader in mobile opens altogether.

Here at Data Axle, we don’t think the open rate is necessarily dead, but it is going to evolve from a concrete metric (sometimes the sole metric email marketers rely on) to a loose metric that can guide campaigns alongside other metrics. In other words, marketers will need to lean on other metrics outside of solely the open rate.

This is a pivotal moment in email marketing history that demands adaptation from email marketers if they want to continue to achieve success with their campaigns (and, importantly, be able to track and optimize that success).

What You Need to Know

What do you need to know now that Mail Privacy Protection is in place? Here are the key points to keep in a mind as a part of this update:

  • You have less insight into the true open rate of each email campaign.
  • You need to be measuring inbox placement rates (i.e., deliverability).
  • You need to evolve your list hygiene and segmentation strategies.
  • You need to include additional metrics for measuring engagement.
  • You need to monitor email testing capabilities—such as send-time optimization and subject line and A/B testing—for changes (or even obsolescence).
  • You must have a subscriber preference center.

Double Down on Deliverability

So, why is deliverability going to be so important going forward? In short, we know that about 20 percent of emails don’t reach client inboxes—which means there’s a lot of room for measurable improvement in this area. Deliverability tools, such as Data Axle’s Inboxable, are not affected by the Mail Privacy Protection and can help provide a new North Star to email marketers in lieu of open rate optimization. Through deliverability insights, Data Axle can help marketers understand how iCloud users behave and give insight to how they place within the inbox—regardless of the iOS 15 changes.

What You Need to Do

So, in addition to doubling-down on deliverability measurement, what should you do to adapt your email strategy for Mail Privacy Protection? Now that Apple’s much-anticipated update is live, here are a few concrete steps you can take to continue to set your email campaigns up for quantifiable success, including improvements in deliverability:


  • Assess the first-party data you’ve collected from your current customers/subscribers for possible changes (such as first/last name, location, shopping preferences). Remember that any data you can use to create more relevant emails will lead to increased relevancy and higher click rates.
  • Define a list-cleansing process for inactive audiences.
  • Re-evaluate the data you ask for at the time of subscription. Preference centers are mandatory!
  • Analyze how many subscribers use Apple Mail to open your emails.
  • Consider real-time data hygiene on any higher-risk opt-in sources.


  • Analyze the use of CTAs within your emails. Employ more CTAs for measuring interest tracks and less CTAs for emails focused on driving engagement.
  • Leverage a welcome email series for gathering subscriber first-party data.
  • Document any creative which is relying on open or pixel-gathered data.


  • Measure deliverability and use it to drive aspects of your email strategy.
  • Define subscriber engagement using clicks, conversions, etc, by type of campaign. For example, base communications (such as newsletters and offers), triggers, lifecycle communications (such as welcome and activation) and loyalty.
  • Analyze click and conversion rates pre- and post-iOS 15.
  • Determine thresholds for how long you can mail new subscribers without click engagement before sunsetting them as “never active.”
  • Re-evaluate the metrics driving your reactivation programs

Additional Steps to Take

Once you have taken the steps you absolutely NEED to take, consider the below. Going the extra mile will keep you a cut above the rest as advertisers adapt to our new privacy-centric world.

Step 1: Assess your email quality
First, you’ll want to rank your email subscribers by quality into low-, medium- and high-quality categories using their subscription source or a data hygiene status.

  • Subscription source: Where did the email opt-in come from? For example, a confirmed opt-in would likely be ranked as high quality, a single opt-in would be medium, and an email append would be low.
  • Data hygiene status: Did the email pass an email hygiene check at the point of collection?

Step 2: Define your engaged subscriber
Next, determine which email data points can be used to define an engaged subscriber list. Review your email data from before the implementation of the iOS 15 update to confirm how these data points have defined your various email audience segments:

  • Opt-in date
  • Clicks
  • Email Conversion rate

Step 3: Define additional subscriber segments
In this step, you should look to define additional segments like inactive, lapsed, highly engaged and other subscriber groups. Layer on additional customer data points available to you that better define a subscriber or customer to your business:

  • Purchase data
  • Site visits
  • SMS
  • First-party data
  • Loyalty program flags


While Apple’s iOS 15 updates have much-needed privacy as their focus, we also know that most subscribers today are willing to provide personal information to brands they know and trust in return for more relevant and personalized communications. So above all, now is a time for marketers to stay on top of email best practices. That starts by monitoring deliverability and ensuring every communication you send is relevant and worthy of your subscribers’ inboxes.

Natasia Langfelder
Content Marketing Manager

As Content Marketing Manager, Natasia is responsible for helping strategize, produce and execute Data Axle's content. With a passion for writing and an enthusiasm for data management and technology, Natasia creates content that is designed to deliver nuggets of wisdom to help brands and individuals elevate their data governance policies. A native New Yorker, when Natasia is not at work she can be found enjoying New York’s food scene, at one of NYC’s many museums, or at one of the city’s many parks with her two teacup yorkies.