Email open rates are a useful, if imperfect, indicator of how engaged your email audience is with your content. When viewed alongside other indicators of email success, like high click-through rates and low bounce rates, open rate data can help you effectively gauge the health of your mailing list.

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How are email opens tracked?

Every email blast that you send automatically includes a tracking pixel in the content of a email. While this pixel is too small to be visible to the email recipient, we are able to tell when the image has been loaded on the recipients' end.

However, because this type of activity tracking requires that images be displayed to the recipient, opens will not be tracked for recipients who have images disabled. Several email clients disable images by default, which makes open data inherently a little unreliable.


Additionally, late in 2021, Apple Mail introduced a "Privacy Protection" feature that disrupts traditional email open tracking by recording a false open for every email delivered to an Apple Mail inbox. We can distinguish between these email-client-generated opens and real ones, so we exclude the fake ones from open stats.

Why do some recipients have an unverified open status?

When we receive an email-client-generated (fake) open activity for a recipient, we record that activity as "open unverified." We will not know if the recipient actually opened the email unless they click on a link within it or open the message in a separate email client that is not privacy protected in this way.

If the recipient does either of these things, their activity will be recategorized from "open unverified" to "opened." Once an open activity has been recorded for a recipient, it cannot become unverified.

Fake open activity will be recorded over time, often in batches, so you may notice recipients in the "unopened" tab later appear in the "open unverified" tab.

How does NationBuilder calculate email open rates?

Because email clients like Apple Mail can generate fake open activity to obscure the recipient's real behavior, we exclude any open activity we receive from recipients with this type of privacy protection enabled from our open rate calculation. This means that your open rate considers only the segment of your recipient list from whom we could track open data.

Anyone who clicks through on an email, even if they have images disabled in their email client or use Apple Mail's Privacy Protection, will be counted as an "open" as well as a "click".

As an example, let's say you send a small test email to just 10 recipients, 4 of whom use Apple Mail's Privacy Protection feature. This means that, of the 10 recipients you emailed (all of whom will appear in the Sent total of your email stats), only 6 of them have trackable open data.

So, if 3 of those 6 recipients open your email, that will result in a 50% open rate.

If 1 of the the 4 Apple Mail recipients clicks a link in your blast, we then know that they also opened your email. Because we now know that they could open an email, they get included in the count of "open rate trackable" recipients.

We can't know whether or not a given recipient will be "trackable" until we receive a fake open activity from them, so the number of privacy protected recipients may also increase over time. If, a couple hours after your 4 opens were tracked, Apple Mail reports 3 additional fake opens for this blast (meaning 7/10 of the original recipients were privacy protected), the resulting open rate would be 100%.

How to use open data to build future recipient lists

Knowing who is engaging with your emails is a critical component of maintaining a healthy email list. While open data isn't perfect, it's a directionally accurate way to tell who is actively engaging with your messaging and who you might need to draw back in.

You can use a variety of filters to identify the recipients you want to target for each audience:

  1. Engaged recipients. A rule of thumb is that anyone who has opened an email in the last 3 months is probably fairly active. We recommend including other activity-based filters (donation history, contact history, etc.) to target your emails further for optimal results. To identify engaged recipients, you can use the filter: Opened email blast from:

  2. Unengaged recipients. If a recipient hasn't opened any emails from you in 3 months or more, it's likely time to reconnect and make sure that they still want to hear from you. This audience will include people whose open tracking has been privacy protected, and may also include recipients whose emails are no longer valid or whose email clients have been filtering your messages into spam folders. To identify unengaged recipients, you can use the filter Opened email blast from and select "has not" from the dropdown menu:

  3. Recipients of unknown email engagement. If a contact has not clicked through on an email in over 3 months or taken any action with your organization, it's probably safe to assume that it's time to check in with them about their email preferences. However, you might decide you want to address your audience of contacts with only unverified open activity separately from other unengaged recipients. If an "unverified open" has been recorded for a recipient, you at least know that your email has reached their inbox.

    To identify this audience, add the results from the Engaged recipients instructions above to a list. Then, run a filter using the criteria Open is unverified from and Lists to pull the recipients who have unverified opens and no real opens from that time period:

Related HOWTOs

How to maintain a healthy email list

Understanding email opt-ins and unsubscribe links

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