Why don't you just use a better email client? I use Eudora and it saves all my attachments in a directory of my choice. It saves only the email message itself in a database like file just like outlook but attachments go into that directory.
It is also safer to use, exploits for outlook won't work with Eudora.
You can use it for free in sponsored mode which means just a small banner in the corner of the main window.
Look at: http://www.eudora.com
Another great email program is 'the bat'. It also stores the attachments in a directory rather than in the message and also much more secure than outlook. Look at: http://www.ritlabs.com/en/products/thebat/