Microsoft Outlook Express stores email files in a hidden data folder buried deep in the user's home folder. It makes it nearly impossible to selectively backup your data files unless you know exactly where it is. I can't tell you how many people have lost years worth of email because they didn't consider delving into this hidden directory.

While Microsoft won't win any usability awards anytime soon, this design is a booby trap. What reason is there for hiding incredibly such information?

  • I can't tell you how frustrating it is to have a reasonable question closed. How in God's earth is this question opinion based? While no one here gave a definitive answer, it doesn't mean an answer doesn't exist. What if one of the developers on the Outlook Express team had an answer, but it now locked?
    – user148298
    Jan 6, 2022 at 23:29

3 Answers 3


The rationale behind this:

  • Documents contains files that can be manipulated by the user - Rename, Edit, Delete, Send etc.
  • ApplicationData (now ProgramData) are files manipulated by software.

You don't open an MSOE file from windows explorer, you should not rename it, to forward an email you do not send the file it is stored in, if you don't need the emails anymore you shouldn't delete that file.

Now, I have marginally better things to do than to defend the clunkyness and "moving target"-ness of who-stores-what-where on Windows. The storage model attempts to solve

  • a slowly evolving model for multiple users on one machine
  • roaming profiles
  • files to big for roaming profiles

So for each file, you'd have to decide: is it user-specific or shared? Is it "owned" by the user, or the software? If it's user specific, does it roam? That's six locations already (shared doesn't roam)

It is exacerbated by various issues:

  • an awkward balance between protecting and enabling the end user
  • users are not administrators - not because security, but skill
  • a "users are administrators" tradition in Windows Development
  • Backward compatibility for "screw that documentation, I find the path myself" developers
  • Backward compatibility with fundamental shifts in working and use models
  • Apparent loss of central control of such issues
  • I still don't understand how can "protect" the user from either self harm, system harm or admin harm?
    – user148298
    Jan 6, 2022 at 23:35

Besides that MS approach to UX makes me scratch my head sometimes, I think that in this case the reason might have been that user should not actually fiddle with the file. He or she should use mail, and not care about the underlying structure.

  • Yeah, but they pretty much leave everything else open including the system32 files, etc.
    – user148298
    Feb 17, 2013 at 5:27
  • And this is exactly what makes me wonder if there is such idea or not. It's like Maeda's simplicity law in a very hostile and complicated world. Could be as well: "Joe, should we have it in My docs?" "Naaah, let's hide it to make them search a bit". There is however an idea behind the file structure, you can read more here: technet.microsoft.com/en-us/library/cc775560(v=ws.10).aspx (old MS paper, regarding Windows Server, but it's pretty much the same in all Windows). Feb 17, 2013 at 6:43
  • @JoelRodgers: more or less, at least XP's explorer had "this folder is off limits" for system drive, program files and windows. Not sure if this is stil in W8, I get rid of those practically automatically.
    – peterchen
    Oct 10, 2013 at 10:01

Windows systems is not intended to backup individual application files, as you are suggesting. Instead you are supposed to backup your computer where you have several options on choosing which user files you want to backup.

Backing up e-mail through selecting an individual application file is an highly advanced task, and I imagine that Microsoft doesn't want that to happen. But if you want to you can.

I'd suggest using the export function instead of fiddling with an application file. Are you sure that you can restore mails if the system fails using your backup? I've seen systems failing if you used it the wrong way. In this case, there might bu a GUID you're unaware of?

To conclude: Backup the system or export e-mails as Microsoft want you handle backup.

  • I'm well aware of how to perform a backup. I was wondering why they hid the folder. Even a systems administrator wants to know where their folder is hidden.
    – user148298
    Mar 3, 2013 at 19:05

Not the answer you're looking for? Browse other questions tagged or ask your own question.