You can't. Masking of phone numbers is hard coded and based on your default
dialing location.
--
Russ Valentine
> Outlook should NOT Automatically insert area codes in contacts!!! How do I
> disable this feature???
[quoted text clipped - 5 lines]
> link to open the suggestion in the Microsoft Web-based Newsreader and then
> click "I Agree" in the message pane.
http://www.microsoft.com/office/community/en-us/default.mspx?mid=1ab5e266-ab
ca-43a0-ac75-56d6a29b5823&dg=microsoft.public.outlook.contacts