What is the type ahead feature?
The type-ahead feature in Outlook uses the names of people to whom you have recently sent emails to populate a list of email addresses that display when you are completing an address. This feature stores in memory a list of names that are used most frequently, and then displays those names at the top of the list.
How does it work?
When you start typing the name, you will start getting a list of names that match your text entered, and the more text that you enter the list will start getting smaller until you find the name that you want. When you find the name that you are looking for, then just press Enter and the name will be added.