Email open rate: measuring who actually reads your emails

Open rate is the percentage of delivered emails that recipients opened. The formula: unique opens divided by delivered messages, multiplied by 100. Ten thousand delivered, 2,300 opened — that's 23%.

How opens are tracked

The standard method is a tracking pixel, a transparent 1x1 image embedded in the HTML body. Each pixel has a unique identifier tied to a specific recipient and campaign. When the mail client loads images, the pixel request hits the sender's server and records an open.

The method has gaps. Opens go uncounted when image loading is disabled, when someone reads in plain-text mode, or behind a corporate firewall blocking external images. On the flip side, antivirus tools or mail servers that pre-fetch images for security scanning can record an open that never happened.

Apple Mail Privacy Protection

In September 2021, iOS 15 shipped with Mail Privacy Protection (MPP). MPP routes all image requests through Apple's proxy and loads them at delivery time, before the user touches the message. For the sender, this looks like an open regardless of whether the recipient ever saw the email. Around 50-60% of Apple Mail users have MPP on. In B2C lists heavy with Apple devices, open rates jumped 10-15 percentage points overnight with no change in actual behavior.

The upshot: open rate alone is not a reliable engagement signal anymore. CTR, conversion rate, and reply rate tell you more about real interest.

Benchmarks by industry

• E-commerce: 15-25%
• SaaS and IT: 20-28%
• Media and publishing: 22-30%
• Education: 25-35%
• Finance and insurance: 20-27%

Transactional emails — order confirmations, password resets — typically hit 60-80% because people are waiting for them.

Open rate and deliverability

Gmail weighs engagement, including opens, when deciding inbox placement. Consistent opens build sender trust. Ignored emails do the opposite: filters route them to spam, which depresses opens further, which makes the problem worse.

What moves open rate

Subject line is the biggest lever. The recipient sees the subject, sender name, and preheader before deciding whether to open. A recognizable sender name beats a generic noreply address. Send time matters too: an email arriving at peak hours competes with a dozen others. And none of it matters if the message lands in spam — list quality is the foundation everything else sits on.