Fax numbers showing when trying to send mail

I'm using Outlook 2002/XP on WinXP

Most of my business contacts have both an e-mail address and fax number.

When I want to send an e-mail, and click the "To..." button, a list of my contacts is shown. However, for each business contact, two lines appear : one for e-mail, the second one for fax.

How do I get Outlook to diplay only the names with e-mail addresses ? I'm not interested in fax numbers when I'm trying to send mail.