You should also have a icon for your corporate email address somewhere on your screen. If you can't see it, make sure it isn't hidden--click the menu button (the one with the BB logo on it) and select Show all.
Then you can hide the messages icon so that you can't see it. (highlight it and then click the menu button and select Hide). The messages folder is a "catch all" for all messages but each account should have it's own folder as well.