Nobody really used other email client besides Outlook and outlook express to activesync. Maybe you would like to check with their support.
Suggestion: Have you tried not installing Outlook, set the MSN 8 as a default email client. Then install Activesync and then sync your Pocket PC with the mail client opened. I would guess since activesync could not detect outlook, it will set the MSN 8 as a sync PIM conduit.
Of course this is a suggestion which I have not tried.
