HiddenArchive automatically saves every incoming and outgoing message to your hard disk. The saved Message File has an .msg Extension, so simply double click the .msg File to open it again in Outlook.
With this Add-In you can ensure that for example every message which comes in or goes out is stored for archiving purposes in case the message accidentially gets lost (deleted) in Outlook.
The best thing is that you will not even notice that HiddenArchive is active. No additional buttons or menu items are being displayed.