"The problem is not limited to just Outlook Express.
Most programs -- word processors, spreadsheets, databases -- save
user data in a proprietary format. They tend to be similarly
generous with importing and stingy with exporting. Many offer the
option to save in a standard, publicly defined format, but often
these do not preserve 100 percent of the formatting or data.
It's no mystery why every application wants to be a data sink;
it's a competitive advantage to lock users into your proprietary
format. But users are suffering, prevented from manipulating their
own data as they see fit.
Worse, in the future, users may have access only to the data
files, with no ability to run the program that originally created
them. Programmers seeking to reverse-engineer the format of a
particular application can use that application to save various
pieces of data and observe the file that results."