iCloud: Archive email
You can quickly move selected messages from your Inbox to the Archive folder so you can read them at a later date using Mail on iCloud.com. Unlike messages you move to the Trash, archived messages remain in your Archive folder until you delete them.
Select the message or messages in the message list, then click the Archive button in the toolbar.
If you don’t see the Archive button in the toolbar, click the Action pop-up menu in the sidebar, then choose Preferences. In the General pane, select “Show Archive icon in the toolbar.”
You can read archived messages, and then move them into other folders or mark them as junk mail.