Patrick
You are on the right way.
Check if this "new" policy is on the top (so it gets executed first), the first policy which applies to a user is used.
Try then to run the provisioning task as well as Synchronize the Mailboxes.
You should get an "Enterprise Vault" Tab in Outlook on the properties of your folders.
But unfortunately, you will get another problem, then.
If you set the Inbox folder to "not archive", all subfolders won't archive, too, so would have to set those explicit to archive.
My suggestion:
Set the Inbox to "Not Archive" and restructure the User's folder to have the structure like this:
Inbox
- EV Archives
- <folders>
In human words: create a folder named EV Archives (or any name you want), set it to archive E-Mails and move all the folders the user has to this folder.
This way, you only have to set archiving policy on two folders, and the subfolders will inherit it.
Hope this was understandable, if not, just ask :)
Cheers
Michel