As you type an email address into any of the email address field (To, CC, BCC) the Autocomplete function checks addresses you have used in the past and displays those that match what you have started to type. Autocomplete is switched on by default.
Do not rely on the autocomplete function to remember addresses you use/need frequently. All important addresses should be stored in your Contacts.
Begin typing an email address. A list of matches will be shown in a drop down list.- Use the mouse to click on the address you wish to use.
To remove an entry that is no longer valid:
Click the cross at the right hand side of the address.