How to open Outlook Express backup .dbx file?
It is almost impossible to extract DBX files manually. However you can use some special soft.
MiTeC Mail Viewer
Open the viewer, click on File> Open and browse to the location of the .dbx file you saved. Select the .dbx file and click open. The top window will list the emails, just select the one you want and the message header will appear in the lower window. With the message selected, click File and then Message view. You can then see the message.