Email Open Rates After Mail Privacy Protection.

The problem

Since Apple Mail Privacy Protection (MPP) launched in 2021, open rates have become meaningless as a performance metric for most senders. MPP pre-fetches images for Apple Mail users regardless of whether they opened the email, inflating reported opens to 50-80% on lists with heavy Apple-skew.

Four years in, most email teams still haven't updated their playbooks. We analyzed 68 client email programs to understand what metrics actually track engagement in a post-MPP world.

Headline findings

What's actually useful post-MPP

1. Click-through rate (CTR)

CTR is the single most useful aggregate engagement metric now. It's measured server-side and isn't affected by MPP. However, CTR benchmarks need to be interpreted alongside send strategy — teams that reduce send frequency often see CTR increase as a proportion of a more engaged list.

Across our dataset, median CTRs:

• Welcome flow emails: 8.4%
• Abandonment flow emails: 11.2%
• Campaign (broadcast) emails: 2.1%
• Post-purchase emails: 4.8%

2. Click-to-conversion rate

What % of email clicks converts to revenue (DTC) or MQL (B2B). Dramatically more useful than open rate for diagnosing which emails work. Low CTR + high conversion = targeted audience, working creative. High CTR + low conversion = clickbait subject lines misaligned with content.

3. List health signals

Rather than open rate, we use a composite "engagement score" for list segmentation:

• Click within last 60 days (weighted highest)
• Site visit within last 30 days (if trackable)
• Purchase within last 90 days
• Open rate (still useful as a tiebreaker, but weighted lowest)

4. Deliverability as a leading indicator

Bounce rates, spam complaint rates, and ISP inbox placement (via tools like GlockApps) are now more diagnostic than open rate for understanding whether your emails are reaching inboxes at all.

Common mistakes we see

• Suppressing non-openers. Suppressing based on open rate removes high-engagement users on Apple Mail. Multiple clients lost 20-30% of engaged subscribers this way.
• A/B testing subject lines using open rate. Subject line tests should measure CTR or revenue, not opens. Open rate differences within MPP-affected segments are noise.
• Reporting open rate to executives as a top-line metric. It's inflated. Report revenue per email, CTR, and list growth instead.

Recommended email KPI stack

• Revenue per email sent (top-line)
• CTR (engagement)
• Click-to-conversion rate (quality)
• List growth net of unsubscribes (health)
• Inbox placement % (deliverability)
• Engaged subscribers (90-day click) (segmentation base)