There is a 2 accounts limit in the free version. The German version of the page tells that the difference between Free and Pro version is, that just 2 EMAIL-accounts can be used in the free version. But the free version also limits using more than 2 email+calendar+contact accounts.
At the moment I am thinking about buying a license, but I am not completely satisfied with some functionality of eM Client, so I also think about reverting back to Outlook.
So the info on the German version of the page is wrong?