Send-Time Optimization (STO)

Using each recipient's past engagement data to deliver email at the time they are most likely to open it.

By Brandon MinaCEO, BrandPilot AIUpdated November 2026

Short answer

Send-time optimization (STO) is the use of each recipient's past engagement data to deliver email at the time they are most likely to open it. Instead of sending to everyone at once, the platform staggers delivery by individual. It can lift engagement modestly, especially for audiences spread across time zones or with varied routines.