If your email account provider sets up the server to delete older messages, the messages are deleted regardless of how you change this option. If you selected None for Trash Mailbox, you can have Mail permanently delete messages automatically. Select a setting other than Never to avoid exceeding storage limits set by your email account provider. Mail erases deleted messages at the specified time. This option is available only for IMAP accounts. Select a mailbox on the mail server or on your Mac to store deleted messages, or choose None (deleted messages are removed and aren’t available in the Trash mailbox).
Mail automatically deletes junk messages at the specified time.
Note: Select this option on each Mac where you’ll use your account, to avoid having two Junk mailboxes in the Mail sidebar.
