Send-time optimisation

Send-time optimisation delivers each message at the hour a given recipient is most likely to open or click, based on their own past behaviour. Teams use it to lift engagement without changing the content, and to spread sending load instead of hitting the whole file at once. It needs enough history per person to beat a sensible fixed send time, so new and dormant contacts fall back to a default. It also breaks genuinely time-bound sends such as flash sales.