isr.co.ro : glossary Inbox The folder or window in an e-mail program that lists incoming messages. With some programs, messages are automatically moved out of the inbox if you read them. In other programs, messages stay until you delete them or move them to another location. A folder or subdirectory where the actual content of incoming messages is stored. Because it may be hidden away within other folders, you may not notice it growing, and unless you clean it out, it may devour your hard disk space.