How Outlook masks phone numbers is based on your dialing location. It is
hard coded and cannot be changed. The only ways I know of to prevent
Outlook's masking of phone numbers are:
1. Enclose the phone numbers in quotes or commas.
2. Set your operating system's dialing location to a null value. Current OS
do not permit you to do this through the GUI.

Signature
Russ Valentine
[MVP-Outlook]
> Outlook Contacts: How can I prevent the automatic bracketing of the area
> code?
> Thank you!