navigation in kmail

Hi, maybe I don't see the wood for the trees, but is there any way to switch to the previous / next message using the cursor up / down keys in kmail as it works for example in mozilla? If I press one of these keys, the view of the currently selected message is scrolled up or down, even if I select a mail header with the mouse. In mozilla, if you click in the display of the current message, cursor up / down scrolls up / down the text of the current message, and if you click on a header of a message in the message list, cursor up / down scrolls up / down the message list... Michael.