Send Time Optimization

Send Time Optimization is an Iterable AI tool that helps you send email and push notifications right when your contacts are most likely to open and read them. For each of a campaign's recipients, it uses machine learning to analyze historical engagement behavior and select an optimal, per-person send time.

For email campaigns, Send Time Optimization attempts to maximize the Email Open Rate (Unique Email Opens or Clicks / Total Emails Delivered) and Email Click Rate (Unique Email Clicks / Total Emails Delivered) metrics.

For push notification campaigns, it tries to maximize the Push Open Rate (Unique Pushes Opened / Total Pushes Delivered) metric.

As you use Send Time Optimization, remember that:

• STO optimizes send times based on project-specific data. It does not analyze cross-project data for the same contact.
• Optimized send times always fall at the top of the hour.
• STO uses a 50/50 control/variation split for Send Time Optimization
• experiments. This is not adjustable.
• For users with insufficient historical project data from which to derive optimized send times, Iterable sends campaigns at their configured send times (even if you've enabled Send Time Optimization).
• Iterable updates its Send Time Optimization machine learning models once per week, using the newest available data for each project and weighting recent data more heavily. All models are updated over the course of the week and not on any set schedule.
• STO does not guarantee higher engagement.
• A rate limit associated with a campaign may cause the campaign to send some messages outside of the STO window.
• If you turn on Quiet Hours and Send Time Optimization 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 Send Time Optimization selects 5:00 a.m. as the ideal send time, but you have quiet hours set from 9:00 p.m. to 9:00 a.m., the campaign will be sent at 9:00 a.m.
• Triggered email and push notification campaigns, and Send Email and Send Push journey tiles, cannot use Send Time Optimization experiments.
• We've tuned Send Time Optimization to account for Apple's Mail Privacy Protection feature.

# Learn more

To learn more about Send Time Optimization, read:

• Creating Blast Campaigns
• Creating Triggered Campaigns
• Creating Variations and Launching an Experiment
• Optimizing Campaign Delivery Times
• Increasing Engagement in Journeys