How can missing suppression logic cause multiple sends?

Missing suppression causes uncontrolled repeat sends:

The failure pattern: Automation has no limit on re-entry. Customer repeats triggering behavior. Each occurrence triggers the automation. Multiple identical sequences start.

Examples: Browse abandonment triggers every time customer browses. No check for "already in browse abandonment flow." Customer receives daily browse abandonment emails. Cart additions without purchase trigger repeatedly.

Required suppressions: Currently in flow: Cannot re-enter same flow. Recently completed: Cooling-off period after completion. Similar flow active: If in related automation, suppress from this one. Maximum entries: Limit total entries over time period.

Implementation: Check suppression conditions at trigger time. Track flow membership and recent history. Build suppression into trigger definitions.

Without suppression, automation treats every trigger as new. Recipients suffer the consequences.