How do you turn typeahead on and off on the client and server?

When does typeahead work on the client? Do you have to turn it on? When does it show the emails address and not the person first and last names? Ie. When I type a persons name when does it revert to the emails address?

Subject: How do you turn typeahead on and off on the client and server?

Here’s some : the Location Document ‘Mail’ tab has settings for this; e-mail addresses will display in the ‘send to’ fields if you select F9 before sending the mail