Engagement scoring drives freshness classification

A binary active/suppressed flag treats a contact who opened an email yesterday identically to one who last engaged 5 months ago. Without intermediate engagement tiers, you cannot implement frequency capping for at-risk contacts, sunset programs for lapsed contacts, or segment-specific content strategies — all of which are proven tactics for preserving list health. Flat lists also make it impossible to diagnose why overall open rates are declining, because you cannot isolate the drag from a growing lapsed cohort. Sending at full frequency to all non-suppressed contacts regardless of recency is a recognized deliverability antipattern that contributes to spam trap hits as dormant mailboxes get recycled.

Implement at least three engagement tiers and recompute them on a nightly schedule:

type EngagementTier = 'active' | 'at_risk' | 'inactive' | 'lapsed'

function computeTier(lastEngagedAt: Date | null): EngagementTier {
  if (!lastEngagedAt) return 'lapsed'
  const days = (Date.now() - lastEngagedAt.getTime()) / 86_400_000
  if (days <= 30)  return 'active'
  if (days <= 90)  return 'at_risk'
  if (days <= 180) return 'inactive'
  return 'lapsed'
}

Store engagement_tier on the contact record and recompute nightly via a bulk UPDATE. Use engagement_tier IN ('active', 'at_risk') in campaign segment queries; route inactive contacts to lower-frequency sends; suppress lapsed contacts from all sends pending a sunset re-engagement.