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.
STO can improve these campaign metrics:
|Email Open Rate
|(Unique Email Opens or Clicks / Total Emails Delivered)
|Email Click Rate
|(Unique Email Clicks / Total Emails Delivered)
|Push Open Rate
|(Unique Pushes Opened / Total Pushes Delivered)
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 at the campaign level and only applies to the campaign you're actively editing.
Optimized send times always fall at the top of the hour.
If a user has less than three months of active user engagement data, Iterable may be unable to determine an optimized send time. In this case, Iterable will send messages at the campaign's configured send time (even if STO is enabled).
Iterable updates STO machine learning models once per week, using the newest available data for each project, weighting recent data more heavily. All models are updated over the course of the week and not on any set schedule.
STO doesn't guarantee higher engagement.
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.
Send Time Optimization accounts for Apple's Mail Privacy Protection feature.
You can't disable STO after Iterable begins sending campaign messages.
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.
If a campaign-triggering API call specifies a specific send time (
sendAt), Iterable doesn't use STO for that send.
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.
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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