Short for mailbox.
The Mbox (mailbox) is the place where all messages and receipts are stored (saved) until they are finally deleted. Folders on the left of the screen segment the mailbox by Saved, Outbox, Trash and Receipts. Each folder can be clicked on to open it and display a list of Contact names. Each contact name contains the messages from (or to) that contact that have come in, gone out or been trashed (since the trash was last emptied).