1). After you have finished typing your email, click “Options” tab (circled in red below).

2). In the “Options” tab, select the “…” (circled in red below).

3). From the drop-down menu, select “Delay Delivery” (shown below)

4). A “Properties” window will appear. In this window, under the “Deliver options” section, select the date and time that you would like the message to be sent. This will be in the option labeled “Do not deliver before” (circled in red).

Once the date and time are set, click Close and proceed to send the message as you would normally. The message will then be in your drafts until it sends at the specified date/time.
 

FAQ

What if I need to change the date that the email is going to send or modify the email?

After you have scheduled the email to send, it is placed in the Drafts folder.
Once you have located the email that you’ve scheduled and selected it, click the Pop Out button in the top right (shown below)

This will open the draft in a fully editable mode where you can modify your message or change the scheduled time (steps 2-4).