Send Time Optimization (STO) is an Iterable AI feature that helps send email and push notifications when your contacts are most likely to engage with them. For each campaign recipient, STO analyzes historical engagement behavior and selects an optimal, per-person send time.
In this article
How Send Time Optimization works
As you use STO, remember that:
STO optimizes send times based on project-specific data. It does not analyze cross-project data for the same contact.
STO is enabled for a single campaign and only applies to the campaign you're actively editing.
Iterable updates STO machine learning models once per week.
Although STO doesn't guarantee higher engagement, it may improve the Email Open Rate, Email Click Rate, and Push Open Rate campaign metrics.
STO accounts for Apple's Mail Privacy Protection feature.
NOTE
If the STO option isn't available, your Iterable project doesn't have enough engagement data. This is common for staging and test projects. Try switching to a project with more engagement data or wait until your project has built up enough data.
Send time considerations
STO sends campaigns as described here:
Optimized send times always fall at the top of the hour.
When an optimized send time increases through the specified window and peaks after the window ends, STO sends the message at the end of the send time window.
If a user has less than three months of active user engagement data, and Iterable can't determine an optimized send time, messages are sent at the campaign's configured send time (even if STO is enabled).
A rate limit associated with a campaign may cause a campaign to send some messages outside of the STO window.
If you turn on Quiet Hours and STO for a campaign, and the ideal send time for a user falls within your Quiet Hours window, your send won’t be optimized—it will be held until the Quiet Hours window ends. For example, if STO selects 5:00 a.m. as the ideal send time, but Quiet Hours is set from 9:00 p.m. to 9:00 a.m., the campaign will be sent at 9:00 a.m.
If a campaign-triggering API call specifies a specific send time (
sendAt), Iterable doesn't use STO for that send.
STO experiments
You can use STO with or without an STO experiment. Without one, Iterable uses STO for all of the campaign's recipients. With an experiment, STO uses a 50/50 control/variation split for STO experiments. This isn't adjustable.
STO can be used with blast campaigns—triggered email and push notification campaigns, and Send Email and Send Push journey tiles, can't use STO experiments.
For more information, see Creating a Send Time Optimization test.
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