How do I A/B test sending frequency?

Frequency testing requires longer timeframes and different measurement approaches than content tests:

Assign segments to different frequencies: One group receives weekly emails, another receives twice weekly, another receives daily. Maintain assignments over extended periods.

Measure over time: Frequency effects compound. Short tests miss long-term engagement decay or unsubscribe accumulation.

Track multiple metrics:

Per-email engagement (opens, clicks). Cumulative engagement over the test period. Unsubscribe rates and complaints. Long-term revenue or lifetime value.

Watch for fatigue signals: Declining open rates over time, increasing unsubscribes, complaint spikes.

Consider segment differences: Optimal frequency varies by engagement level. Your most active subscribers may tolerate more.

Frequency testing answers "how much is too much." Push until you find the point of diminishing returns.