How does “send-time optimization” work in automation?

Send-time optimization (STO) uses data to deliver emails when individual recipients are most likely to engage:

How it works:

The system analyzes each recipient's historical engagement patterns: when they open emails, click links, or make purchases. Instead of sending all automated emails immediately, it holds messages and releases them at optimal times for each individual.

Data sources:

Email open timestamps. Click activity timing. Purchase time patterns. Website visit timing.

Implementation approaches:

Machine learning models predicting optimal windows. Rules-based logic using engagement history. Time-zone-aware delivery defaults.

Tradeoffs:

Delays time-sensitive automations. Requires sufficient engagement history per recipient. May not help for new subscribers without data.

Send-time optimization trades immediacy for relevance. For some automations, that trade makes sense. For others, immediate delivery matters more.