If you get the following message for FOLDERS.DBX when trying to “compact all folders” in Outlook Express
The folder is currently in use by Outlook Express or by another application.
there is a simple solution. The error message is deceptive since the actual cause has nothing to do with being in use. The problem occurs when you try to compact all folders and not all folders are actually present on disk. This can happen if a .DBX file got deleted somehow (for example if you decided to save some space by deleting the .DBX files of empty folders.) When OE tries to compact, it checks the folders.dbx file to see what .DBX files to expect, and when it can’t find one, it complains with the inaccurate message above.
The fix is simple, just replace or recreate the files. The easiest way to do this is to simply open the missing folders in OE because it will automatically create a .DBX file if one does not exist.
If you do not know which ones are missing, you can click on “Local Folders”, press the * key on the keypad to expand all branches, then click on each and every folder—you could also use the Down key instead of clicking, but then you have to wait a second on each folder for OE to open them, clicking opens them instantaneously.
After you’ve ensured that all .DBX files exist, you can successfully compact all folders.