Files with the extension DBX contain a folder of the email program Outlook Express from Microsoft. The name of the file usually represents the name of the corresponding folder in the program, eg Sent.Dbx or inbox.Dbx (for the Inbox). The format of these files is proprietary and can be processed by only a few programs.
The file folder.Dbx contains a directory (index) of the other folders and is generated automatically. Copying the files or the directory in which they are located copies the entire structure of the Outlook Express folders and the emails they contain. This makes it very easy to create a backup copy of your own emails.
Extracting individual messages is more complicated, but Outlook Express itself and a number of programs are capable of doing so. These often have special functions such as the reconstruction of partially destroyed mails or the migration of data.