Scheduling is done when creating the email.
Click on the Settings tab at the top menu bar.
Scroll down to the Send time section, and choose Schedule for later.
In the dialog, select the desired date and time.
4. When the email is ready, click Review and Schedule at the top right corner to activate the scheduling.
A scheduled email cannot be edited as long as it is in a "Scheduled" state. If you want to edit your scheduled email, you first need to cancel the scheduling.
Cancel a scheduled email
A scheduled email can be canceled at any time until the scheduled date and time occur. To do so, open the email to choose Remove scheduling and edit.
When a scheduled email is canceled, it returns to the "draft" state and can be edited as any other email.