OFFICE 365 - REMOVE ADDRESSES FROM THE AUTO-COMPLETE LIST
Many clients have the ability to remember what addresses you have sent messages to, this is known as your auto-complete list. Sometimes you may enter the wrong address for a recipient or the recipient changes their address. The steps below will guide you through the process of removing an address from this list.
Important: Your auto-complete list is not backed up. If you delete an entry or remove all entries from the auto-complete list, there is no way to recover this.
Removing an address from your auto-complete list
In Outlook on the web, click the New button to start composing a new email.
In the To: field, start typing an email address.
Using the up and down arrows on your keyboard, select the email address you would like to remove from the suggested contacts list. Either press the Delete key on your keyboard or the X beside the email address you wish to delete.