Enabling STO on a single activity is a few clicks. The setup work is in deciding which sends benefit and which should stay immediate.
- Confirm Einstein STO is enabled at the BU
Marketing Cloud Setup, Einstein, Send Time Optimization. The feature must be enabled at the business unit level before activities can use it.
- Open the email or SMS activity in Journey Builder
Inside the journey, click the message activity to open its configuration panel.
- Switch delivery to Send Time Optimization
Under the Delivery section, change the option from Send Immediately to Use Send Time Optimization. The 24-hour window controls appear below.
- Configure the optimization window
Pick a window aligned with business constraints (full 24 hours for most marketing sends, narrower for time-sensitive content). The wider the window, the more lift STO can produce.
- Activate the journey and measure with a holdout
Activate. Run an A/B holdout on the first major send to confirm lift. Once confirmed, leave STO on for similar activities without re-testing each one.
The default. Maximum room for STO to optimize. Best for evergreen marketing content with no deadline.
Constrains STO to a daytime range. Useful when brand voice requires daytime delivery or when SMS rules apply.
Excludes Saturday and Sunday. Sometimes required for B2B audiences or compliance reasons.
Contacts with insufficient engagement history fall back to a population-level recommendation, typically mid-morning local.
STO is configured per activity, so the same journey can mix STO marketing nurture with immediate transactional sends.
- Narrow optimization windows reduce STO lift. A 2-hour window gives the model almost nothing to work with. Default to the 24-hour window when business constraints allow.
- STO cannot rescue time-sensitive content. Event reminders and flash sales with hard deadlines should send immediately, not via STO.
- Contacts with thin engagement history fall back to the population default. STO has little impact on a new subscriber's first three sends.
- STO measures timing lift, not content lift. A campaign with weak content will underperform whether STO is on or off; do not blame STO for content problems.
- Per-recipient send time changes when the journey re-enters the activity. A contact who completes the journey twice will likely get the two messages at different hours.