Outlook for Mac 2011 – deactivate exchange accounts without loosing data locally

I have 9 different email accounts set up in my Outlook.  2 of these (both exchange accounts) are no longer active, so I want to find a way of "deactivating" these, so the do not try to access the server each time I start Outlook.

The information in these accounts is critical though, so I do not want to "play around" risking loosing all the locally stored messages.

What is the best/correct way to do this...?

/AnBe