iCloud: Save or open a draft email
Messages are saved automatically when you use Mail on iCloud.com. Each time a message is saved, the new draft overwrites the previous one.
To open a message that you were previously working on, select the Drafts folder in the sidebar, then double-click the message.
When you send a message, the draft version is removed from the Drafts folder.
You can save space in your iCloud Mail mailbox by deleting draft messages you don’t plan to send.