What is a DBX file, and how do I open it?

Outlook express logo.
Outlook Express logo
Outlook Express logo.

Microsoft Outlook Express was (and still is) a very popular free email client distributed Microsoft Windows operating systems from Windows 98 though  XP. As of this writing, despite its age Windows XP remains the most widely used desktop operating system on planet earth (according to Hitslink, in May 2012, XP had 44% of the Windows market share, compared to Windows 7’s 40.5%).

Despite its age, there are still millions of people using Outlook Express, even though has been replaced in the Windows Vista operating system with Windows Mail, which in turn was replaced by Windows Live Mail in Windows 7.

Outlook Express stores email messages and newsgroups in .DBX files, which reside in the Store folder on your hard drive.
The store folder can be located by starting Outlook Express and then selecting Tools>Options>Maintenance.
Outlook Express will create a separate .DBX file for each email inbox and newsgroup. For example, Inbox.dbx indicates the incoming mail folder.
A  DBX file is a complex database, and it can’t be opened simply by double clicking on it. It is a compilation of many individual email records and file attachments and should be imported into another application that has the specialized ability to read MBX files. The MBX file structure is a proprietary Microsoft invention, and there have been attempts over the years to decode it.
If you need to open a MBX files without Outlook Express you will require a viewer or some other specialized software, such as DBXAnalyzer  by DI Management, capable of parsing the DBX file structure revealing its contents.
Outlook Express DBX files have been notorious over the years for becoming corrupted during compaction, or if the size of the file becomes too great.  This problem was so common that it has driven a large market for Outlook Express email recovery software.
Outlook Express does not support encryption of the DBX file, although it does support password protection. Many users erroneously believe that adding a password to an Outlook Express DBX file also provides encryption.
While many people have moved on from Outlook Express to Windows Mail or Outlook, there are still millions who rely on this aging email client. Even as Outlook Express is eventually retired with Microsoft XP, the ability to decode DBX files will still be necessary in order to retain a record of email communication, making .DBX file viewers a useful addition to your app portfolio.