The HC warmup imported ~1000 fresh providers/day into a persistent segment list
(list 10), but each day's campaign targeted that WHOLE cumulative list -- so the
cohort imported on day 1 received the identical 'Free NPI Check' email every
subsequent day (verified: subscriber 3410 got campaigns 38-42, 5x). Program-wide
that was 23,843 sends to 6,587 people (3.6x avg, max 30x) and blocklisted ~12%
of the list -- a Yahoo 'user complaints' deferral now confirms the burn.
Fix: import each day's slice into a dedicated dated SEND list and bind that day's
campaign to ONLY that list, so every provider gets exactly one send. The
persistent segment list is still used for dedup/records. ensure_campaign now
matches the exact dated name (never reuses a prior day's campaign/slice).
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