In Caching mode, you can delete items, retract items, and empty the Trash the same way you would in the Online mode.
Click the item in your Mailbox.
Click
> .If you’re deleting an outgoing item, click one of the available options.
To free up disk space, click
> .This permanently removes all deleted items from your Caching Mailbox.
Changes in your Caching and Online Mailboxes will automatically synchronize.