Simple IT help: Outlook 2010 Clean Up greyed out

I was archiving my e-mails when I happen to find that my Clean up and Ignore functions in Outlook 2010 is greyed out. Here's some info:

You have to enable your CEM (Cached Exchange Mode) from the Account Settings. I am using a shared PC so I seldom put it on cached mode. I wonder why there is a need to activate that to get the function so I Google for answers and here's what they say:

Hi,

Quite a number of the new features rely on the local Outlook data store. This means that when you are using an Exchange account, you will need to enable Cached Exchange Mode (CEM) for them to work.

As said, there are quite a number of features in Outlook 2010 that require Cached Exchange Mode in order for them to work or to work better. The most notable features are;