Not an option. Masking of phone numbers is hard coded in Outlook by design.
It must remain consistent. It is up to your synchronization software to
create the correct format for your phone.

Signature
Russ Valentine
[MVP-Outlook]
>I would like to turn off the auto formatting of phone numbers in the phone
> book. I am having trouble with mobile numbers being turned into land
> numbers
> and creating double entries when synchronising with other applications.