Open rates used to be the primary way that marketers measure the success of an email marketing campaign. But with several key updates in email clients, this once golden metric has become unreliable. We’ll break down what’s changed—and what metrics we recommend you rely on instead so you can make data-driven decisions for your campaigns.

There are a few reasons open rates have become unreliable.

Apple’s Mail Privacy Protection automatically “opens” emails in the background to protect user privacy. These auto-opens show up in reports as if a real person opened the email, so they add noise to the data. This inflates the open rate and makes it hard to tell if a subject line actually influenced more people to open the email. In fact, it can even make strong-performing subject lines look less impressive—because when the overall open rate is artificially high, it’s harder to show a meaningful lift from the subject line test.

Many corporate entities scan emails for threats, “opening” them to check for malicious content. This can also skew open rates data: the opens are from bots, not consumers.

Some email clients allow recipients to preview emails without opening them—resulting in false positive “opens.”

Even without reliability issues, open rates only measure if an email was opened, not whether the recipient took a desired action. Think of it this way: an email could be opened and then immediately deleted!

We recommend focusing on what people actually do after receiving the email—like clicking or converting—so we can measure real impact. We optimize our content to CTR and conversions because these metrics better measure the ultimate objection of most emails (a purchase, signup, etc.).

(# of Unique Clicks) / (Total Delivered) x 100 = Click-Through-Rate

The CTR is usually the easiest way to determine the effectiveness of the body content of an email. CTRs vary depending on the type of campaign and the quality, creativity, and relevance of the copy. They’re also influenced by the subject line, even if nothing changes in the body. This is due to what we call "intent" at Persado, meaning that the customer is influenced by the subject line in a way that once they've read it, they've already made a decision and have the intent to either click or not click, regardless of what's in the body.

For that reason, the CTR is often the preferred engagement metric when evaluating both the subject line and body content.

(# of Unique Conversions) / (Total Delivered) x 100 = Conversion Rate

Conversion rates are generally the holy grail of email metrics because they are the ultimate objective of most promotional and eCommerce emails. Depending on the campaign, conversions could mean purchases, sign-ups, or leads generated. This important email marketing metric may have multiple steps, such as form pages in a shopping cart, so there could be intermediate conversion events leading up to the final, revenue-driving KPI. Normally if they’re available, this metric is the best measure of success for any email campaign with a conversion goal.