Use the Mail app on your Mac to move, delete, or copy iCloud email
If you use the Mail app for your iCloud email, you can move or copy email messages from iCloud to your computer, or you can simply delete them from iCloud.
Move or copy email from iCloud to your Mac
Moving your messages from iCloud to your computer can be useful when your iCloud mailbox is full, or you want to reduce the amount of iCloud storage you're using. Follow these steps to move messages from iCloud and store them on your Mac instead.
In Mail, choose Mailbox > New Mailbox.
A New Mailbox dialog opens. Choose On My Mac from the Location pop-up menu, then enter a name for the new mailbox. Click OK.
Select your iCloud inbox from the list of mailboxes in the sidebar, then select the messages to move.
To move the messages, drag the messages you selected to your new mailbox. Or choose Message > Move to > your new mailbox.
To copy messages, hold down the Option key while dragging the messages you selected to your new mailbox. Or choose Message > Copy to > your new mailbox.
If you want to make a backup copy your entire iCloud mailbox, including every message and folder in the mailbox:
Select your iCloud inbox from the list of mailboxes in the sidebar. If iCloud mail is the only email account you use, your iCloud inbox might be named Inbox. If you have multiple email accounts, you might need to click the arrow next to All Inboxes to reveal the inbox for each account, including your iCloud account.
Choose Mailbox > Export Mailbox.
Choose a destination folder for the mbox archive, then click Choose to save it.
Delete messages from iCloud
Follow these steps to permanently delete messages from iCloud without keeping a copy on your computer.
Select your iCloud inbox from the list of mailboxes in the sidebar.
Select the messages to delete, then press Delete or choose Edit > Delete. The messages are moved to your Trash folder in iCloud.
Choose Mailbox > Erase Deleted Items to permanently delete the messages in the Trash folder.
