Open Rate

What Is Email Open Rate?

Email open rate is the percentage of successfully delivered emails that were opened by recipients, calculated as (unique opens / delivered emails) × 100. Historically, opens were tracked by embedding a tiny invisible image (tracking pixel) in the email — when the email was opened and images loaded, the pixel fired and recorded an open. Today, open rate measurement is complicated by Apple's Mail Privacy Protection, which pre-loads email content (including pixels) regardless of whether the user actually opens the email.

The Apple MPP Problem

Apple's Mail Privacy Protection (MPP), launched in 2021, has significantly inflated open rates for senders whose recipients use Apple Mail. MPP causes Apple Mail to pre-fetch all email content — including tracking pixels — through Apple's proxy servers, before the user opens the email. This creates a "phantom open" that looks like a real open but isn't. For many B2C senders, 30-60% of their audience may now be using Apple Mail, making open rate an unreliable metric for that segment.

Open Rate as a Deliverability Signal

Despite measurement challenges, open rates remain important as a deliverability signal. ISPs like Gmail use engagement data — including opens — as an input to spam filtering decisions. Higher aggregate open rates (across all recipients at a given ISP) signal that your mail is wanted and belongs in the inbox. Lower open rates signal that recipients aren't interested, which over time can push mail toward the spam folder. Even if you can't measure opens precisely, optimizing for genuine engagement still matters.

What Affects Open Rate

Subject line quality — the single largest factor in whether an opened email gets opened. From name recognition — recipients open from senders they recognize and trust. Send timing — sending when recipients are most likely to be checking email. Inbox placement — you can't open what lands in spam. List quality — invalid and disengaged addresses never open. Segmentation — relevant email gets opened; generic email doesn't. Each of these levers can meaningfully move open rates.

Open Rate Benchmarks

Industry-average open rates vary widely by sector and audience. B2C retail typically sees 15-25%. B2B SaaS sees 20-30%. Transactional email (receipts, notifications) sees 40-60% because recipients are expecting and looking for these messages. These benchmarks are useful for context but should be interpreted cautiously given MPP inflation. The more meaningful benchmark is your own historical trend — are opens going up or down relative to your own baseline?

List Quality and Open Rate

Sending to invalid or disengaged addresses directly suppresses your open rate — they add sends to the denominator (delivered emails) without adding opens to the numerator. Removing invalid addresses and re-verifying your list with EmailVerify.io improves your open rate by ensuring only potentially engageable contacts are in your denominator. Combined with engagement segmentation (focusing sends on active contacts), this is the most reliable way to improve open rate metrics. Start at emailverify.io.