Outlook 2007: Click New > Mail Message.
To delete a single cached entry: In Outlook: If the nickname cache becomes corrupt, Outlook may not be able to identify recipients, may offer incorrect recipients, may send to an incorrect or old email address, or may send the message to the wrong person. The nickname list is automatically compiled as you address email messages. Outlook maintains a 'nickname' list that is used by both the automatic name checking and the AutoCompletion features.
