Send Time Optimization (STO) works only with recurring and batch programs. If you enable it for transactional email it will simply be ignored.
When STO is enabled for an email node, the incoming contacts are treated in the same way that STO treats batch campaigns:
- A random control group of 10% is created and the launch times for the rest of the launch list are calculated.
- On the next even hour after calculation, the email is sent to the control group and the first STO launch group.
- The campaign is sent to the rest of the STO launch groups every two hours, over the next 24 hours.
The main difference in behavior is that all contacts are queued at the email node until the final launch has been sent, at which time they are all free to progress along the program once again.
We are monitoring the effect that large numbers of STO launches on the same environment have on email sending. Until we are absolutely certain that there is no risk of performance loss, we will be limiting the total number of launches that can use STO at any given time. If this happens, you will receive a message in the Send email node and in the Notification Center.
Turning Send Time Optimization (STO) on
Send Time Optimization works only with recurring and batch programs.
You can only enable STO in a program if its state is In design. You cannot turn STO on or off once the program's state has been changed from In design to another one.
To enable or disable STO in an active program, you have to pause or end it, then copy it to create a new program. Now you can turn STO on or off in the new program.
Cancelling Send Time Optimization (STO)
Pausing or freezing an Automation Center program will not stop STO emails that are already scheduled for launch. If it is still critical to abort the STO launch, contact Emarsys Support to abort your emails.