Open rate was the primary cold email metric until Apple Mail Privacy Protection launched in 2021 and inflated reported open rates by 15-30 percentage points for any list with Apple Mail users. In 2026, open rate is still useful for relative comparison but is not a reliable absolute benchmark. This guide covers what open rate actually means, why it’s broken, industry benchmarks with Apple MPP context, and which metrics matter more.
Apple Mail Privacy Protection (MPP), introduced in iOS 15 and macOS Monterey in September 2021, routes email content through Apple’s proxy servers and prefetches remote content - including tracking pixels - before the user ever opens the email. This causes email marketing and cold email tools to record an “open” for every Apple Mail user, regardless of whether they actually read the email.
In B2B cold email to US and European audiences, approximately 40-60% of recipients use Apple Mail as their primary email client. This means reported open rates in most tools are artificially inflated by 15-30 percentage points. A reported “55% open rate” may reflect a true open rate of 25-40%. The inflation makes it impossible to use open rate as an absolute benchmark or to reliably A/B test subject lines using open rate as the success metric.
| Email type | Reported open rate | Estimated true open rate | What to benchmark against |
|---|---|---|---|
| B2B cold email | 35-65% | 15-35% | Reply rate (3-5% = good) |
| B2B newsletter / nurture | 40-55% | 20-30% | Click rate + reply rate |
| Transactional (receipts, notifications) | 50-70% | 40-60% | Delivery rate + click rate |
| B2C newsletter | 20-35% | 15-25% | Click rate + unsubscribe rate |
| Cold email follow-ups | 25-50% | 10-25% | Reply rate on follow-up only |
The most reliable signal for cold email. Every reply required both reading and motivation. Not inflated by Apple MPP or bot activity. Track weekly, target 3-5% for cold email.
Replies expressing interest - not opt-outs or negative responses. Most directly correlated with pipeline generated. Target 0.5-2% of total sent.
Emails that could not be delivered. Under 2% for cold email. Above 3% means list quality is damaging domain reputation and everything else downstream.
The business outcome. Target varies by ACV - typically 0.3-1.5% of total emails sent results in a booked meeting.
Gmail’s direct signal of how your sending domain is perceived. High = inbox. Medium = risk. Low = spam. Check weekly in Google Postmaster Tools.
% of recipients who mark your email as spam. Under 0.1% is the safe threshold. Above 0.1% triggers deliverability deterioration at Gmail.
Open rate is still valid for relative comparison between two campaigns sent to the same audience at the same time - if Campaign A has 45% open rate and Campaign B has 60%, Campaign B’s subject line is likely stronger, even if the absolute numbers are inflated. It is also useful for detecting severe deliverability drops - if open rate falls from 55% to 20% overnight, that signals a deliverability problem rather than a subject line issue. Use open rate as a diagnostic signal, not as an absolute performance metric.
High bounce rate harms domain reputation, which reduces inbox placement, which makes all other metrics worse. Fix it at source - verify before every campaign. 100 free credits, no card required.
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