The same email can succeed or flop depending on when it lands. Send-time optimization aims to hit each subscriber's inbox at their personal sweet spot, rather than blasting everyone at once.

How does send-time optimization work?

It analyzes each subscriber's historical engagement — when they typically open and click — and schedules their send for that window. Some tools do this automatically per subscriber.

Why does send time matter?

An email that arrives when someone is checking their inbox gets seen; one buried under later messages gets ignored. Optimizing timing can lift opens and clicks with no content changes.

Send-time best practices

Use data over generic "best time" rules, account for time zones, and test. For behavior-triggered emails, timing is anchored to the action, which is often ideal already.