Brainstorm how to optimize email engagement

You own lifecycle emails and must increase on‑site engagement attributable to email. a) Define a single primary objective metric and 2–3 guardrails (e.g., unsubscribe rate, spam complaint rate, session depth). b) Generate at least 10 concrete interventions across targeting, timing, content, and system levers (e.g., send‑time optimization, subject/body variants, frequency caps, personalized recommendations, reactivation cohorts, triggered vs batch, pre‑header tests, multi‑subject holdouts, copy length, AMP/email actions); for each, estimate expected lift and risks. c) For your top two ideas, design robust experiments: control/holdout construction to measure incremental lift vs no‑email and vs status‑quo, traffic allocation, deliverability controls (bounces, spam placement), contamination mitigation, sequential testing or MDE‑based duration, multiple‑comparison handling, and long‑term retention readouts. d) List instrumentation/data you need (deliveries, opens, clicks, device, locale, user email eligibility, prior activity) and how you’ll detect cannibalization with push/notifications. e) Prioritize with RICE/ICE and propose a safe ramp if early wins move the primary metric but harm a guardrail.