Related Questions:
Send emails in the future
Schedule my emails
Contact my Clients at a later date
Can I edit a scheduled email?
Procedure:
Compose an Email to send (Steps can be found here)
Scroll to the bottom of the email and click on the Send Later? checkbox
Use the date picker to select a date and time for the email to be sent
Click Send Later button
After choosing Send Later, it is not possible to edit the email. The only available option is to delete it and begin again. Therefore, it is advised to double-check the email before sending.