The way that Outlook works is that it shows both the email and the fax
addresses in your contact list. Therefore if you have a contact with both
entries completed then it will appear more than once in you contact list
when addressing.

I you do not wish to display the fax entry when addressing then prefix the
fax number with a non-numerical character (e.g. FAX: ) and this will prevent
the fax entry from displaying but still visible when you view the Contact
item.

If you have a number of these to change or wish them to be managed
automatically when you create a new contact then have a look at WS:Fax
Display Manager from Websetters (www.websetters.co.uk) to manage for you.

Regards
Graeme