Archive email in Mail on iCloud.com
You can quickly move messages you want to save to the Archive folder to help keep your Inbox from getting too cluttered. Unlike messages you move to the Trash, archived messages remain in your Archive folder until you delete them.
In Mail on iCloud.com, do one of the following:
Select the message, tap the Move to Folder button , then choose Archive.
Select the message, then tap the Archive button in the toolbar.
If you see the Delete button in the toolbar instead of the Archive button , tap 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.