EEAX can archive your emails in six different ways with further sub-options.
One of the features of EEAX is to archive emails as native Entourage file format.
The files with .eml extensions give you the possibility to restore one email or group of emails simply drop them back to Entourage at any time. This will ensure to restore the email archived even with the future versions of Office.
Archived emails and attachments are automatically indexed by OS X.
You can search inside thousands of files instantly using the power of Apple Spotlight technology or using SpotInside. Find anything, anywhere, fast.