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.
uChecker helps keep open rates healthy by removing invalid and inactive addresses before you send. Emails reach real recipients, engagement stays up, and inbox providers treat your campaigns better for it.
Why the number stopped meaning what it did
Apple Mail Privacy Protection, introduced in 2021, pre-fetches tracking pixels for every message regardless of whether the recipient looked at it. Apple Mail accounts for a large share of consumer mail, so a meaningful slice of your reported opens are machines, not people.
The effect is not evenly spread, which is worse than a uniform inflation: a B2C list skewed toward iPhone users looks far healthier than a B2B list on Outlook, and the two are no longer comparable.
What to measure instead
Click-through rate survives, because a click requires intent. So does the conversion rate on whatever the message asked for. For list hygiene, engagement over a long window — did this address click anything in six months — is a sturdier signal than any single-campaign open figure.
Open rate still has one honest use: comparing two subject lines within a single A/B test on the same list at the same time, where the machine-open inflation applies equally to both arms.