It squirrels them away in a hidden system folder, with one of those registry-like hash names.
This article may be of use:
http://support.microsoft.com/kb/270670
If you want to get the actual database files themselves, this site should be useful:
http://www.computerhope.com/issues/ch000457.htm
Outhouse Express is a truly terrible program that you should look into replacing. I hear that Thunderbird has become decent lately.