NeuralSend looks at your recipients' interactions, derives their location, industry, gender and a number of other relevant factors and then returns the best time to send your email to them.
NeuralSend is the default option on the Auto-Send Email Play step.
Set NeuralSend as Your Default Send Option
From your personal settings (Menu > Settings > Email) toggle this setting "ON".
Note: Even with this setting enabled, you will have the option to send any email instantly while on an email task.