Inbox Minimalism

Do you ever get a letter in your letterbox, read it, then put it back in the letterbox? If you work in an office with mail trays, do you ever put a document back in the same tray after treating it? The digital equivalent to these practices is keeping mail in our inboxes and outboxes, which has become common practice and is encouraged, with email providers boasting of their (increasingly) ample memory size.