Mistake: leaving open-tracking pixels on at scale

Mistake: leaving open-tracking pixels on at scale
Open-tracking injects a 1x1 image and rewrites links through a tracking domain. Both are classic spam fingerprints, and since Apple Mail Privacy Protection fakes opens anyway, your data is garbage on top of hurting placement.

The fix: turn off open tracking entirely for cold; keep click tracking only if you rotate a clean custom tracking domain. Instantly and Smartlead both default open-tracking ON — flip it off per campaign.

Pros / Cons of killing opens:
— Pro: removes an injected image, a known filter trigger
— Pro: stops you optimizing toward fake Apple opens
— Con: you lose 'opened but didn't reply' segmentation
— Con: harder to justify subject-line tests to a boss who wants open rates

Verdict: 4.5/5. Reply rate is the only metric that survives MPP anyway.

Who it's for: anyone still A/B testing subject lines on open rate in 2026.