The following options are available:
saving an email as a draft while you are composing the email
sending a saved email draft
How to save an email as a draft:
In the Compose new email window, click on Save.
Result: The email is saved in the Drafts folder.
How to send a saved email draft:
Open the Drafts folder.
Select an email draft in the side bar.
Click on Edit in the display area.
Complete the entries. Click on Send.