Send time optimization (STO) is a feature that is used to manage the scheduling time to send an SMS. This feature selects the optimal time for each recipient, which maximizes the engagement possibilities. This article explains the calculation of the optimal time, the current limitations of the tool and how to consult the distribution for the sending times.
Required plan: Grow or Boost |
How is STO Calculated?
The system analyzes the different times that each recipient has interacted (views and clicks) with SMS in the past 3 years. The STO is calculated according to the moments a contact opened an SMS (views) or clicked links in SMS. For example, if a recipient has clicked 3 times at 8:00, 4 times at 12:00 and 5 times at 16:00, the STO for that contact will be 16:00. The calculation uses only the views from humans, whether you use the Exclude views from bots option or not.
The system uses the recipient's time zone to determine the ideal send time. The area code of a contact is used by the system to determine which time zone to use if no time zone is specified for that contact.
→ Verify the time zone configuration for the project
Rules when there is no data (fallback)
If a contact does not have sufficient engagement data, the system will send the SMS at the average optimal time for the other contacts of the project, or if there is insufficient data in your project, use a predefined time for your industry.
Exception for France
France imposes restrictions on SMS sending times. A contact, whose optimal time is in the forbidden times, will receive the SMS a little before or after, depending on which is closer. Thus, a contact with an optimal time at 21:00 will receive the SMS before the forbidden period.
Consulting STO Distribution Before Sending
Before sending your SMS, you can consult a report for the optimal times for all the contacts. This report shows an overview of the optimal times (for example, 8:00-9:00, 10:00-11:00, etc.). 
The preview times could be different from the actual sending times if you have contacts in France (see the restrictions for France).
Current Limitations
1. No limit on send time
At the moment, you can't define limit times. It means that, if a contact has no specified time zone, that contact could receive the SMS outside of "standard" times (8:00-20:00), except for France, which has restrictions on SMS sending times. However, the optimal send time is always using the results of the contact's behavior.
2. Sendings programmed for the same day
If you approve a sending for the same day, contacts who have an optimal time that is already past on that day, will receive the SMS immediately instead of the STO. The other contacts will still receive the SMS at their STO. It can happen that the SMS provider delays the delivery for different deliverability reasons. Unfortunately, we don't have control over this aspect.
If the time zone in your project is configured to adapt for each contact, you must approve the sending early enough in the day to cover all the time zones of your contacts (an error message will warn you if the sending time is already passed in some time zones). To avoid that a sending time is passed in a contact's time zone, it is better to program the sending at least the day before.
3. Sendings approved after the programmed date
If a sending using an STO is approved after the selected date, contacts will receive the message immediately, independently from the STO.
4. Engagement data dependence
The efficiency of STO is based on the quality and quantity of engagement data about contacts. For new contacts or those who rarely or do not interact with your SMS, the STO will not be precise.
STO in Automated Campaigns
You can use STO for an SMS included in an automated campaign. To activate the STO, go to the additional options for that SMS:
Then, check the STO option: