Changed batch file behaviour

For good reasons that I do not need to go into now, I have been SUCCESSFULLY backing up my emails daily from Outlook Express 6, with a batch file that, amongst others, contain the lines :
<<copy "C:\...\Outlook Express\today.dbx" C:\Data\_Mail\today>>
<<copy "C:\...\Outlook Express\folders.dbx" C:\Data\_Mail\today>>
In very recent times, response to those lines has changed, so that \today\ no longer ends up containing just a copy of today.dbx and of folders.dbx, but ALSO newly created 11Kb DBX files for EVERY folder in \Outlook Express\. Why would this change have occurred, and more importantly, how can I get back to the state where only today.dbx and folders.dbx are copied ?