Apple Mail Privacy Protection accounted for in open rate calculation

Apple Mail Privacy Protection (MPP), rolled out in iOS 15, proxy-loads tracking pixels through Apple CDN servers the instant an email arrives — before the recipient ever opens it. This inflates measured open rates by 30–60% for audiences with significant iOS or Apple Mail usage, silently corrupting the engagement signals your send-time optimization, list segmentation, and campaign ROI calculations depend on. Campaign decisions made on these numbers — suppressing disengaged contacts, picking a winning A/B variant by open rate, or attributing revenue to high-open-rate sequences — all degrade in quality. The data-integrity taxon is directly implicated: the metric exists but measures something fundamentally different from human engagement.

Filter MPP bot opens at ingest time by checking the AppleMailDoPre user-agent and persisting a machine_open boolean on every event row. Add the flag in your pixel or webhook handler:

const isMppBot = (userAgent: string | null): boolean =>
  userAgent?.includes('AppleMailDoPre') ?? false

async function recordOpen(
  contactId: string,
  campaignId: string,
  userAgent: string | null
) {
  await db.emailEvents.insert({
    type: 'open',
    contact_id: contactId,
    campaign_id: campaignId,
    machine_open: isMppBot(userAgent),
    user_agent: userAgent,
    occurred_at: new Date()
  })
}

Then query open rates using WHERE machine_open = false. Expose both the filtered and raw rate in your reporting UI so the distinction is auditable.