
Firstly,
do not mistake in understanding Outlook Express and Outlook as same
program, both of these are different program and have different
functionalities. Microsoft Outlook saves its file in PST file and
Outlook express saves its file in DBX file. It you have to open DBX
file then you have to open Outlook Express first. DBX Files are
stored in store folder of Outlook Express. It should be opened only
in Outlook Express. If it is opened manually then the Express file
may get corrupted and it will start showing problem in its working.