Disabling Auto Archive in Outlook 2013 via GPO

Hi! I've been trying to disable auto archive feature for Outlook 2013 via GPO. I successfully did it for Outlook <2013, but I can't get it working with this edition.

I've downloaded ADMX templates from http://www.microsoft.com/en-us/download/details.aspx?id=35554 and copied them in our central AMDX repository (\\\SYSVOL\\Policies\PolicyDefinitions). In fact I see the policy in GPO editor.
I've set to "Disabled" Microsoft Outlook 2013\Outlook Options\Other\AutoArchive\AutoArchive Settings, but no avail. As test purposes, I've set "Disable File|Archive" to enable, but still nothing.
gpresult on the client states that the GPO is applied, and in event viewer it report that applied successfully n changes.

BUT the final result isn't accomplished.

By the way, I've looked in http://technet.microsoft.com/en-us/library/cc178992.aspx for the relative registry key, but... uh-ho, "AutoArchive Settings" (this is how it is written in the admx template) it's not present! All I can see, comparing the registry for Outlook 2010 on my PC and the one for Outlook 2013 on other PCs, those are much more empty than mine (for Outlook 2010 we set up exactly the same policies as for 2013).

Has anyone faced this issue before and know the solution? This is the first time we used ADMX templates, so maybe there is something I did wrong there.

PS: I don't know if it matters, but in GPO editor I see all Outlook 2013 policies written in English (I think because Windows 2008 is in English) but clients I'm testing are mainly Italian. ADML pack for Italian language is copied in PolicyDefinitions\it-it.
Might this matter?

Thank you very much!