Joel Lindstrom of CustomerEffective is the first CRM MVP to provide an article on the Resource Center. It is titled, "Categorizing tracked e-mail in Microsoft Dynamics CRM".
"You are a busy professional who sends and receives a large quantity of e-mail messages. Fortunately, you have Microsoft Dynamics CRM, so you track these messages from Microsoft Office Outlook and associate them with the account, contact, or opportunity that they pertain to.
But say that you want to further categorize these e-mail messages, so that when you look through a mile-long list of e-mails on a contact record, you can see those tagged as, for example, "Product Question."