Problems with Mail on macbook pro

Hi,

I have problems with Mail on Macbook Pro.

When I open Mail it tells me that the application is active. But when I click on the icon in the dock no window opens. Nothing happens. I doesn't even update incoming mails.

I have only been able to open a window with the shortcut '⌘0'. But it's like the accounts are inactive. Unread mails wont mark as read and I can't get the new mails from my inbox, it just looks like so:

When I go to preferences I can't really tell if I should adjust some stuff. I haven't made any changes lately myself så I don't know why this is.

Hope to get some clearifying answers. Thanks!

/SB