Frequency capping
A rule limiting how many emails a recipient receives in a defined period — protects against fatigue and unsubscribes.
Frequency capping is the practice of limiting how many emails a single recipient receives within a defined time window. Common policies: no more than 3 emails per week, no more than 1 email per day, no more than 5 promotional emails per month. Caps are enforced across all campaigns and triggers, so a recipient already in a welcome series doesn't also get a newsletter blast the same day.
The math of frequency capping is straightforward: every additional email beyond optimal cadence lowers per-message engagement and accelerates unsubscribes. The optimal cadence varies by audience — power users tolerate more, casual users less — but the per-list optimum is rarely above 3 messages per week for most B2B audiences.
Most ESPs support frequency caps at the global, segment, and message-type levels. Configuration is one of the highest-leverage levers operators have, and one of the most ignored. A list that's being over-mailed by 50% will recover engagement within 2-3 weeks of cap enforcement, no other changes needed.