But if you're not using it, why can't you just delete "Outlook Email" from the email client, eh? That sucker is just an empty void that you skip over to get to your real email accounts and alas, WM won't let you just delete it. Curses!
Simply back up your device or that registry value and delete the \Activesync folder, followed by a soft reset. Bam, no more "Outlook Email" folder to skip over.
Update: Yeah, people are having, um, varying results with this one. Use at your own risk. And be sure to back up your phone first.