Open Rate

Open rate is the percentage of recipients who open an email relative to the number of emails actually delivered. It is one of the most widely used metrics in email marketing because it shows, at first glance, how compelling the subject line was and how healthy your sender reputation is. It is normally measured as unique opens (each person counts once even if they open several times) over emails delivered, not over emails sent.

The formula is simple: open rate = (unique opens / emails delivered) × 100. For example, if you deliver 10,000 emails and 2,300 different people open them, your open rate is 23%. As an early behavioral metric in the conversion funnel, it works as a gauge of interest: a healthy open rate enables the next step, which is the click and then the conversion.

In marketing automation, open rate is one of the indicators that Revio monitors and optimizes across every campaign and automated flow, along with deliverability and the segmentation of each audience.

How it is really measured (and why it is an imperfect metric now)

Historically, opens have been tracked with a tracking pixel: an invisible 1x1 image that the email client downloads when the recipient opens the message. That download tells the platform an open happened. The problem is that this technique depends on images loading, and that no longer always happens reliably. Since Apple Mail Privacy Protection (MPP), launched in 2021, Apple preloads the pixel on its servers even if the user never opens the email, which artificially inflates opens. The effect shows up in the numbers: according to Brevo (2026), the average campaign open rate in Latin America goes from 14.72% to 23.28% when those automatic opens are counted. That is why open rate overreports, and it is best read as a trend, not as an absolute figure.

Why it still matters

Despite the noise, open rate is still the first actionable indicator of a campaign. A sudden drop usually points to three concrete things: a weak subject line, a deliverability problem (you are landing in spam) or a degraded list (old or cold contacts). Before looking at conversions, a good marketing team checks opens to know whether the message was even seen. It is also a signal that feeds lead scoring: someone who opens regularly is warmer than someone who never does.

What counts as a good open rate

There is no universal number; it depends on the industry, list quality and type of send. As a reference, these are the averages Brevo measures with data from more than 175,000 customers (for campaigns, excluding Apple MPP automatic opens):

A transactional email gets opened far more than a promo because the recipient is expecting it. That is why you should never compare a newsletter's open rate with that of an order confirmation: they reflect different intents.

How to improve it (concrete levers)

• Subject line and preheader: they are the only thing visible before the open. Test variants with A/B testing and measure which one lifts opens.
• Recognizable sender: a "From" with a person's or brand's name gets more opens than a cold noreply@.
• List hygiene: clean out bounces and inactive contacts. A clean list improves deliverability and, with it, the real open rate.
• Timing and frequency: match the send time to your audience's behavior.
• Segmentation: sending the right message to the right group raises relevance and opens.

Common mistakes

The most frequent one is obsessing over open rate as if it were the goal. Opens do not pay the bills: they are a means, not an end. Another mistake is comparing pre- and post-MPP open rates as if they were the same thing; Apple's change broke the historical series. A third is not separating unique opens from total opens, which lumps one person who opened ten times together with ten people who opened once. Finally, many teams watch open rate but ignore the bounce rate, when a high bounce rate is precisely what drags opens down.

Open rate vs click-through rate

These two metrics are often confused, but they measure different things at different points in the journey.

More and more teams prioritize CTR and conversion rate over open rate, precisely because opens have become noisy. An example: an Argentine SMB that sends its monthly newsletter sees a 28% open rate but only a 1.5% click rate. The subject line works, but the content does not hook readers. Without looking at both metrics together, it would have celebrated a good campaign that did not actually move the business.