Auto-complete email address problem in Windows Mail

Besides the contacts list, Windows Mail keeps a separate list of the last 29 addresses you've sent to, which is the list used for auto- completion. That list is kept in the registry, and is not readily accessible for editing. If you need to edit or avoid the auto-completion, need to edit the registry.If you are comfortable with editing the registry,

key is:
HKEY_CURRENT_USER\Software\Microsoft\Windows Mail\Recently Used Addresses

I would simply delete that key instead of trying to edit its data values.