Email Send Time Optimization

Send Time Optimization (STO) is a feature that uses an algorithm to find the best time to send the campaign to the subscribers in the next 24 hours based on their engagement history.

Why do we need STO?

STO enables you to adapt your campaigns to individual usage patterns of your subscribers. Your emails will be more likely to show up at the top of the inbox and more likely to be engaged with. 

How to enable STO?

After creating your email campaign, click the Enable Send Time Optimization box in the launch step and your email will be sent to customers at the best time.

How does it work?

STO logs the engagement metrics of each subscriber for 1-hour slots in a day (which makes 24 slots in total).

Take, for example, Jane Doe as a subscriber.

{
	"1": {
		"clicks": 1,
		"opens": 2
	},
	"2": {
		"clicks": 0,
		"opens": 1
	},
	...
	...
	...
	"24": {
		"clicks": 3,
		"opens": 2
	}
}

For each time slot, the optimality score is calculated by giving weight values for opens and clicks. Opens have a weight of 0.4 and clicks have a weight of 1.

The time slot that has the highest optimality score is recorded as “optimal emailing hour” for that subscriber. The example of 00.00 has the score of 3.8 (3x1 + 2x0.4) and will be chosen as an optimal emailing time for Jane Doe.

Whenever Jane opens or clicks an email, her slots will be updated and her optimal time will be recalculated.

Deep Insights

What happens if the subscribers does not have any past events such as opens or clicks?

The campaign will be sent right away.

When are the time-optimized emails sent?

These emails are sent at the beginning of each time slot.

Can STO be used in A/B campaigns?

This feature is not supported in A/B campaigns.

Can STO be used in recurring campaigns?

Currently, this feature is not offered for recurring campaigns.

Does STO count  days of the week while calculating the scores?

The day of the week is not counted in this calculation.

What happens if two slots have the same score?

The previous optimal hour is not updated until a new one comes up with a higher score.

What happens when Jane opens/clicks an email after her emails are set for the STO campaign? Is her optimal time for this campaign updated?

It is not updated. The campaign will be sent regarding her optimal time while her STO campaign is being set.

Can STO be used when an automated warm-up is enabled?

STO is not supported during the warm-up period.