Frequently Asked Question
How to Clear the Whole Auto-Complete Cache
In the Outlook main window, click the File menu.
From the File menu, click the Options button.
In the Options, click the Mail tab and scroll down to the Send Messages section.
Click the Empty Auto-Complete List button.
A confirmation box will appear, click Yes. You will need to close Outlook and reopen it and then Auto-Complete cache will be completely erased.