Outlook Express has can be used as a picture viewer.
When posting to a newsgroup, then a header is also sent which contains of who actual sent the news post.
Outlook Express Address Book stores the addresses in a WAB file, which one can backup and restore.
Outlook Express stores the emails in DBX files, which one can backup and restore.
How to put the company name in the title of the Outlook Express application.
Changing Outlook Express to open emails in the Restricted Security zone to improve security.
Outlook Express can be used by malicious worms and virus to spread themselves using malformed HTML emails.
The splash screen can be useful to see if an application is actually starting, but it can also be disabled.